RD Sharma Class 12 Solutions Chapter 10 Differentiation - Other Exercise
Differentiation Excercise: 10.4
Differentiation exercise 10.4 question 1
Answer:
$\left(\frac{-y}{x}\right)$Hint:
Use product rule to find
$\frac{dy}{dx}$Given:
$x y=C^{2}$Solution:
Differentiate the given equation
$x y=C^{2}$ w.r.t x
$\begin{aligned} &x \cdot \frac{d y}{d x}+y=0 \\ &x \frac{d y}{d x}=-y \\ &\frac{d y}{d x}=\frac{-y}{x} \end{aligned}$ $\left[\begin{array}{c} \because \frac{d(\operatorname{cons} \tan t)}{d x}=0 \\ \frac{d(u \cdot v)}{d x}=u \cdot \frac{d v}{d x}+v \frac{d u}{d x} \end{array}\right]$Hence
$\frac{d y}{d x}=\frac{-y}{x}$ is the required answer.
Differentiation exercise 10.4 question 2
Answer:
$\frac{(x+y)^{2}}{y^{2}-2 x y-x^{2}}$Hint:
Use product rule to find
$\frac{d y}{d x}$Given:
$y^{3}-3 x y^{2}=x^{3}+3 x^{2} y$Solution:
Differentiating the given equation w.r.t x
$\frac{d}{d x}\left(y^{3}-3 x y^{2}\right)=\frac{d}{d x}\left(x^{3}+3 x^{2} y\right)$$\frac{d}{d x}\left(y^{3}\right)-\frac{d}{d x}\left(3 x y^{2}\right)=\frac{d}{d x}\left(x^{3}\right)+\frac{d}{d x}\left(3 x^{2} y\right)$$3 y^{2} \frac{d y}{d x}-3\left[x \frac{d y^{2}}{d x}+y^{2} \frac{d x}{d x}\right]=3 x^{2}+3\left[x^{2} \frac{d y}{d x}+y \frac{d x^{2}}{d x}\right]$ $\left[\because \frac{d(u v)}{d x}=u \frac{d v}{d x}+v \frac{d u}{d x}\right]$$3 y^{2} \frac{d y}{d x}-3\left[x \cdot \frac{d y^{2}}{d y} \times \frac{d y}{d x}+y^{2}\right]=3 x^{2}+3\left[x^{2} \frac{d y}{d x}+y(2 x)\right]$$3 y^{2} \frac{d y}{d x}-3\left[x(2 y) \cdot \frac{d y}{d x}+y^{2}\right]=3 x^{2}+3 x^{2} \frac{d y}{d x}+6 x y$ $\left[\because \frac{d\left(x^{n}\right)}{d x}=n x^{n-1}\right]$$3 y^{2} \frac{d y}{d x}-6 x y \frac{d y}{d x}-3 y^{2}=3 x^{2}+3 x^{2} \frac{d y}{d x}+6 x y$$3 y^{2} \frac{d y}{d x}-6 x y \frac{d y}{d x}-3 x^{2} \frac{d y}{d x}=3 x^{2}+6 x y+3 y^{2}$$3 \frac{d y}{d x}\left[y^{2}-2 x y-x^{2}\right]=3\left(x^{2}+2 x y+y^{2}\right)$$\frac{d y}{d x}=\frac{3\left(x^{2}+2 x y+y^{2}\right)}{3\left(y^{2}-2 x y-x^{2}\right)}$$\frac{d y}{d x}=\frac{(x+y)^{2}}{y^{2}-2 x y-x^{2}}$ $\left[\because(a+b)^{2}=a^{2}+2 a b+b^{2}\right]$Is the required answer.
Hence
$\frac{d y}{d x}=\frac{(x+y)^{2}}{y^{2}-2 x y-x^{2}}$Answer:
$-\left(\frac{y}{x}\right)^{\frac{1}{3}}$Hint:
Use the differentiation formula of
$\left(x^{n}\right)$i.e.
$\frac{d\left(x^{n}\right)}{d x}=n x^{n-1}$Given:
$x^{\frac{2}{3}}+y^{\frac{2}{3}}=a^{\frac{2}{3}}$Solution:
Differentiate the given equation w.r.t x
$\frac{d}{d x}\left(x^{\frac{2}{3}}+y^{\frac{2}{3}}\right)=\frac{d}{d x}\left(a^{\frac{2}{3}}\right)$$\frac{d}{d x}\left(x^{\frac{2}{3}}\right)+\frac{d}{d x}\left(y^{\frac{2}{3}}\right)=0 \quad\left[\because \frac{d(\operatorname{cons} \tan t)}{d x}=0\right]$$\frac{2}{3}(x)^{\frac{2}{3}-1}+\frac{d\left(y^{\frac{2}{3}}\right)}{d y} \times \frac{d y}{d x}=0 \quad\left[\because \frac{d\left(x^{n}\right)}{d x}=n x^{n-1}\right]$$\frac{2}{3}(x)^{\frac{-1}{3}}+\frac{2}{3}(y)^{\frac{2}{3}-1} \frac{d y}{d x}=0$$\frac{2}{3}(x)^{\frac{-1}{3}}+\frac{2}{3}(y)^{\frac{-1}{3}} \frac{d y}{d x}=0$$\frac{d y}{d x}=\frac{\frac{-2}{3}(x)^{\frac{-1}{3}}}{\frac{2}{3}(y)^{\frac{-1}{3}}}=\frac{-(x)^{\frac{-1}{3}}}{(y)^{\frac{-1}{3}}}$$\frac{d y}{d x}=-\frac{(y)^{\frac{1}{3}}}{(x)^{\frac{1}{3}}} \quad\left[\because(x)^{-n}=\frac{1}{(x)^{n}}\right]$$\frac{d y}{d x}=-\left(\frac{y}{x}\right)^{\frac{1}{3}}$Hence
$\frac{d y}{d x}=-\left(\frac{y}{x}\right)^{\frac{1}{3}}$is required answer
Differentiation exercise 10.4 question 4
Answer:
$\frac{4}{3}\left(\frac{1-4 x+3 y}{4 x-3 y+1}\right)$Hint:
Use chain rule to find the differentiation
Given:
$4 x+3 y=\log (4 x-3 y)$Solution:
Differentiate the given equation w.r.t x
$\frac{d}{d x}(4 x+3 y)=\frac{d}{d x}(\log (4 x-3 y))$$\frac{d}{d x}(4 x)+\frac{d}{d x}(3 y)=\frac{d(\log (4 x-3 y))}{d(4 x-3 y)} \times \frac{d(4 x-3 y)}{d x}$[Using the chain
$\frac{d(f(x+y))}{d x}=\frac{d(f(x+y))}{d(x+y)} \times \frac{d(x+y)}{d x}$ ]
$4 \frac{d x}{d x}+3 \frac{d y}{d x}=\frac{1}{(4 x-3 y)} \times\left[\frac{d(4 x)}{d x}-\frac{d(3 y)}{d x}\right] \quad\left[\because \frac{d(\log x)}{d x}=\frac{1}{x}\right]$$4+3 \frac{d y}{d x}=\frac{1}{4 x-3 y} \cdot\left[4-\frac{d(3 y)}{d y} \times \frac{d y}{d x}\right]$$4+3 \frac{d y}{d x}=\frac{1}{4 x-3 y} \cdot\left[4-3 \times \frac{d y}{d x}\right]$$4+3 \frac{d y}{d x}=\frac{4}{4 x-3 y}-\frac{3}{4 x-3 y} \frac{d y}{d x}$$3 \frac{d y}{d x}+\frac{3}{4 x-3 y} \cdot \frac{d y}{d x}=\frac{4}{4 x-3 y}-4$$3 \frac{d y}{d x}\left(1+\frac{1}{4 x-3 y}\right)=\frac{4-4(4 x-3 y)}{4 x-3 y}$$3 \frac{d y}{d x} \times\left(\frac{4 x-3 y+1}{4 x-3 y}\right)=\frac{4-16 x+12 y}{4 x-3 y}$$\frac{d y}{d x}=\frac{4-16 x+12 y}{(4 x-3 y)} \times \frac{4 x-3 y}{(4 x-3 y+1)} \times \frac{1}{3}$$\frac{d y}{d x}=\frac{1}{3} \cdot \frac{(4-16 x+12 y)}{(4 x-3 y+1)}$$\frac{d y}{d x}=\frac{4}{3} \cdot\left(\frac{1-4 x+3 y}{4 x-3 y+1}\right)$Hence
$\frac{d y}{d x}=\frac{4}{3}\left(\frac{1-4 x+3 y}{4 x-3 y+1}\right)$ Is the required answer
Differentiation exercise 10.4 question 5
Answer:
$\frac{-b^{2} x}{a^{2} y}$Hint:
Use chain rule and differentiation formulas like
$\frac{d x^{n}}{d x}=n x^{n-1}$Given:
$\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1$Solution:
Differentiate the given equation w.r.t x
$\frac{d}{d x}\left(\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}\right)=\frac{d(1)}{d x}$$\frac{d}{d x}\left(\frac{x^{2}}{a^{2}}\right)+\frac{d}{d x}\left(\frac{y^{2}}{b^{2}}\right)=0 \quad\left[\because \frac{d(\operatorname{cons} \tan t)}{d x}=0\right]$$\frac{1}{a^{2}} \cdot \frac{d\left(x^{2}\right)}{d x}+\frac{1}{b^{2}} \cdot \frac{d\left(y^{2}\right)}{d x}=0$$\frac{1}{a^{2}} \times 2 x+\frac{1}{b^{2}} \times\left(\frac{d y^{2}}{d y} \times \frac{d y}{d x}\right)=0 \quad\left[\because \frac{d x^{n}}{d x}=n x^{n-1}\right]$$\frac{2 x}{a^{2}}+\frac{1}{b^{2}}\left(2 y \cdot \frac{d y}{d x}\right)=0$$\frac{2 x}{a^{2}}+\frac{2 y}{b^{2}} \cdot \frac{d y}{d x}=0$$\frac{d y}{d x}=\frac{\frac{-2 x}{a^{2}}}{\frac{2 y}{b^{2}}}=\frac{-2 x \times b^{2}}{2 y \times a^{2}}$$\frac{d y}{d x}=\frac{-x b^{2}}{y a^{2}}$$\frac{d y}{d x}=-\frac{b^{2} x}{a^{2} y}$Hence
$\frac{d y}{d x}=-\frac{b^{2} x}{a^{2} y}$ is the required answer
Differentiation exercise 10.4 question 6
Answer:
$\frac{d y}{d x}=\frac{y-x^{4}}{y^{4}-x}$Hint:
Use chain rule to find the differentiation formula like
$\frac{d\left(x^{n}\right)}{d x}=n x^{n-1}$Given:
$x^{5}+y^{5}=5 x y$Solution:
Differentiate the given equation w.r.t x
$\frac{d}{d x}\left(x^{5}+y^{5}\right)=\frac{d}{d x}(5 x y)$$\frac{d}{d x}\left(x^{5}\right)+\frac{d}{d x}\left(y^{5}\right)=5 \frac{d(x y)}{d x}$$5 x^{4}+\left(\frac{d y^{5}}{d y} \times \frac{d y}{d x}\right)=5\left[x \frac{d y}{d x}+y \frac{d x}{d x}\right]$ $\left[\because \frac{d\left(x^{n}\right)}{d x}=n x^{n-1}, \frac{d(u v)}{d x}=u \frac{d v}{d x}+v \frac{d u}{d x}\right]$$5 x^{4}+5 y^{4} \frac{d y}{d x}=5\left[x \frac{d y}{d x}+y\right]$$5 x^{4}+5 y^{4} \frac{d y}{d x}=5 x \frac{d y}{d x}+5 y$$5 y^{4} \frac{d y}{d x}-5 x \frac{d y}{d x}=5 y-5 x^{4}$$\frac{d y}{d x}\left(5 y^{4}-5 x\right)=5 y-5 x^{4}$$\frac{d y}{d x}=\frac{5 y-5 x^{4}}{5 y^{4}-5 x}$$\begin{aligned} &\frac{d y}{d x}=\frac{5\left(y-x^{4}\right)}{5\left(y^{4}-x\right)} \\ &\frac{d y}{d x}=\frac{y-x^{4}}{y^{4}-x} \end{aligned}$Hence
$\frac{d y}{d x}=\frac{y-x^{4}}{y^{4}-x}$ is the required answer
Differentiation exercise 10.4 question 7
Answer:
$\left(\frac{a y-x-y}{x+y-a x}\right)$Hint:
Use chain rule and product rule
Given:
$(x+y)^{2}=2 a x y$Solution:
Differentiate the given equation w.r.t x
$\frac{d}{d x}\left[(x+y)^{2}\right]=\frac{d}{d x}[2 a x y]$$\frac{d}{d x}\left[x^{2}+2 x y+y^{2}\right]=2 a \frac{d}{d x}(x y) \quad\left[\because(a+b)^{2}=a^{2}+2 a b+b^{2}\right]$$\frac{d\left(x^{2}\right)}{d x}+\frac{d(2 x y)}{d x}+\frac{d y^{2}}{d x}=2 a\left[x \frac{d y}{d x}+y \frac{d x}{d x}\right] \quad\left[\because \frac{d(u v)}{d x}=u \frac{d v}{d x}+v \frac{d u}{d x}\right]$$2 x+2 \frac{d(x y)}{d x}+\frac{d y^{2}}{d y} \times \frac{d y}{d x}=2 a\left[x \frac{d y}{d x}+y\right]$$2 x+2\left[x \frac{d y}{d x}+y \frac{d x}{d x}\right]+2 y \frac{d y}{d x}=2 a x \frac{d y}{d x}+2 a y \quad\left[\because \frac{d\left(x^{n}\right)}{d x}=n x^{n-1}\right]$$2 x+2 x \frac{d y}{d x}+2 y+2 y \frac{d y}{d x}=2 a x \frac{d y}{d x}+2 a y$$2 x \frac{d y}{d x}+2 y \frac{d y}{d x}-2 a x \frac{d y}{d x}=2 a y-2 x-2 y$$\frac{d y}{d x}[2 x+2 y-2 a x]=2 a y-2 x-2 y$$\frac{d y}{d x}=\frac{2 a y-2 x-2 y}{2 x+2 y-2 a x}$$\frac{d y}{d x}=\frac{2(a y-x-y)}{2(x+y-a x)}$$\frac{d y}{d x}=\frac{a y-x-y}{x+y-a x}$Hence
$\frac{d y}{d x}=\frac{a y-x-y}{x+y-a x}$ is the required answer
Differentiation exercise 10.4 question 8
Answer:
$\frac{y-4 x^{3}-4 x y^{2}}{4 y x^{2}+4 y^{3}-x}$Hint:
Use chain rule and the product rule of differentiation
Given:
$\left(x^{2}+y^{2}\right)^{2}=x y$Solution:
Differentiate the given equation w.r.t x
$\frac{d}{d x}\left[\left(x^{2}+y^{2}\right)^{2}\right]=\frac{d}{d x}(x y)$$\frac{d}{d x}\left[\left(x^{2}\right)^{2}+\left(y^{2}\right)^{2}+2 x^{2} \times y^{2}\right]=x \frac{d y}{d x}+y \frac{d x}{d x} \quad\left[\because(a+b)^{2}=a^{2}+2 a b+b^{2}\right]$[Product Rule
$\frac{d(u v)}{d x}=u \frac{d v}{d x}+v \frac{d u}{d x}$]
$\frac{d}{d x}\left[x^{4}+y^{4}+2 x^{2} y^{2}\right]=x \frac{d y}{d x}+y$$\frac{d}{d x}\left(x^{4}\right)+\frac{d}{d x}\left(y^{4}\right)+\frac{d}{d x}\left(2 x^{2} y^{2}\right)=x \frac{d y}{d x}+y$$4 x^{3}+\left(\frac{d y^{4}}{d y} \times \frac{d y}{d x}\right)+2\left(\frac{d\left(x^{2} y^{2}\right)}{d x}\right)=x \frac{d y}{d x}+y$$4 x^{3}+4 y^{3} \frac{d y}{d x}+2\left[x^{2} \times \frac{d y^{2}}{d x}+y^{2} \frac{d x^{2}}{d x}\right]=x \frac{d y}{d x}+y \quad\left[\because \frac{d\left(x^{n}\right)}{d x}=n x^{n-1}\right]$$4 x^{3}+4 y^{3} \frac{d y}{d x}+2\left[x^{2} \times \frac{d y^{2}}{d y} \times \frac{d y}{d x}+y^{2}(2 x)\right]=x \frac{d y}{d x}+y$$4 x^{3}+4 y^{3} \frac{d y}{d x}+2\left[x^{2} \times(2 y) \frac{d y}{d x}+2 x y^{2}\right]=x \frac{d y}{d x}+y$$4 x^{3}+4 y^{3} \frac{d y}{d x}+4 x^{2} y \frac{d y}{d x}+4 x y^{2}=x \frac{d y}{d x}+y$$4 y^{3} \frac{d y}{d x}+4 x^{2} y \frac{d y}{d x}-x \frac{d y}{d x}=y-4 x^{3}-4 x y^{2}$$\frac{d y}{d x}=\frac{y-4 x^{3}-4 x y^{2}}{4 y x^{2}+4 y^{3}-x}$Hence
$\frac{d y}{d x}=\frac{y-4 x^{3}-4 x y^{2}}{4 y x^{2}+4 y^{3}-x}$ is the required answer.
Differentiation exercise 10.4 question 9
Answer:
$\left[-\left(\frac{x}{y}\right)\right]$Hint:
Use chain rule and
$\frac{d\left(\tan ^{-1} x\right)}{d x}=\frac{1}{1+x^{2}}$Given:
$\tan ^{-1}\left(x^{2}+y^{2}\right)=a$Solution:
Differentiate the given equation w.r.t x
$\frac{d}{d x}\left(\tan ^{-1}\left(x^{2}+y^{2}\right)\right)=\frac{d(a)}{d x}$$\frac{d\left(\tan ^{-1}\left(x^{2}+y^{2}\right)\right)}{d\left(x^{2}+y^{2}\right)} \times \frac{d\left(x^{2}+y^{2}\right)}{d x}=0$ [Using chain rule]
$\left[\because \frac{d(\operatorname{cons} \tan t)}{d x}=0\right]$$\frac{1}{1+\left(x^{2}+y^{2}\right)^{2}} \times\left(\frac{d x^{2}}{d x}+\frac{d y^{2}}{d x}\right)=0$ $\left[\because \frac{d\left(\tan ^{-1} x\right)}{d x}=\frac{1}{1+x^{2}}\right]$$\frac{1}{1+\left(x^{2}+y^{2}\right)^{2}} \times\left(2 x+\frac{d y^{2}}{d y} \times \frac{d y}{d x}\right)=0$$\frac{1}{1+\left(x^{2}+y^{2}\right)^{2}} \times\left(2 x+2 y \frac{d y}{d x}\right)=0$$\frac{2 x}{1+\left(x^{2}+y^{2}\right)^{2}}+\frac{2 y}{1+\left(x^{2}+y^{2}\right)^{2}} \frac{d y}{d x}=0$$\frac{2 y}{1+\left(x^{2}+y^{2}\right)^{2}} \frac{d y}{d x}=-\frac{2 x}{1+\left(x^{2}+y^{2}\right)^{2}}$$\frac{d y}{d x}=-\frac{2 x}{\left[1+\left(x^{2}+y^{2}\right)^{2}\right]} \times \frac{1+\left(x^{2}+y^{2}\right)^{2}}{2 y}$$\frac{d y}{d x}=\frac{-2 x}{2 y}=-\frac{x}{y}$$\frac{d y}{d x}=-\frac{x}{y}$Hence
$\frac{d y}{d x}=-\frac{x}{y}$ is the required answer
Differentiation exercise 10.4 question 10
Answer:
Answer:
$\frac{y}{x}\left[\frac{x e^{(x-y)}-1}{y e^{(x-y)}-1}\right]$Hint:
Use chain rule and quotient rule
Given:
$e^{x-y}=\log \left(\frac{x}{y}\right)$Solution:
Differentiate the given equation w.r.t x
$\frac{d\left(e^{x-y}\right)}{d x}=\frac{d\left(\log \left(\frac{x}{y}\right)\right)}{d x}$$\frac{d\left(e^{x-y}\right)}{d(x-y)} \times \frac{d(x-y)}{d x}=\frac{d\left(\log \left(\frac{x}{y}\right)\right)}{d\left(\frac{x}{y}\right)} \times \frac{d\left(\frac{x}{y}\right)}{d x}$$\left(e^{x-y}\right) \times\left[\frac{d x}{d x}-\frac{d y}{d x}\right]=\frac{1}{\left(\frac{x}{y}\right)} \times\left[\frac{y \cdot \frac{d x}{d x}-x \cdot \frac{d y}{d x}}{y^{2}}\right]$ $\left[\because \frac{d\left(e^{x}\right)}{d x}=e^{x}\right]$[Using quotient rule
$\frac{d\left(\frac{u}{v}\right)}{d x}=\frac{v \cdot \frac{d u}{d x}-u \cdot \frac{d v}{d x}}{v^{2}}$ ]
$e^{x-y} \times\left[1-\frac{d y}{d x}\right]=\frac{y}{x} \times\left[\frac{y-x \frac{d y}{d x}}{y^{2}}\right]$$e^{x-y}-e^{x-y} \frac{d y}{d x}=\frac{1}{x y}\left(y-x \frac{d y}{d x}\right)$$e^{x-y}-e^{x-y} \frac{d y}{d x}=\frac{y}{x y}-\frac{x}{x y} \cdot \frac{d y}{d x}$$\frac{x}{x y} \frac{d y}{d x}-e^{x-y} \frac{d y}{d x}=\frac{y}{x y}-e^{x-y}$$\frac{d y}{d x}\left(\frac{x}{x y}-e^{x-y}\right)=\frac{y}{x y}-e^{x-y}$$\frac{d y}{d x}=\left[\frac{\frac{y}{x y}-e^{x-y}}{\frac{x}{x y}-e^{x-y}}\right]$$\frac{d y}{d x}=\left[\frac{\frac{1}{x}-e^{x-y}}{\frac{1}{y}-e^{x-y}}\right]$$=\frac{\left(\frac{1-x e^{x-y}}{x}\right)}{\left(\frac{1-y e^{x-y}}{y}\right)}$$=\frac{y\left(1-x e^{x-y}\right)}{x\left(1-y e^{x-y}\right)}$$=\frac{-y\left(x e^{x-y}-1\right)}{-x\left(y e^{x-y}-1\right)}$$\frac{d y}{d x}=\frac{y}{x} \cdot\left(\frac{x e^{x-y}-1}{y e^{x-y}-1}\right)$Hence
$\frac{d y}{d x}=\frac{y}{x} \left[\frac{x e^{x-y}-1}{y e^{x-y}-1}\right]$ is the required differentiation.
Differentiation exercise 10.4 question 11
Answer:
$\left[\frac{\sin (x+y)-y \cos x y}{x \cos x y-\sin (x+y)}\right]$Hint:
Use chain rule and product rule
Given:
$\sin (x y)+\cos (x+y)=1$Solution:
Differentiate the given equation w.r.t x
$\frac{d}{d x}[\sin x y+\cos (x+y)]=\frac{d(1)}{d x}$$\frac{d}{d x}[\sin x y]+\frac{d}{d x}[\cos (x+y)]=0 \quad\left[\because \frac{d(\operatorname{cons} \tan t)}{d x}=0\right]$$\frac{d(\sin x y)}{d x y} \times \frac{d x y}{d x}+\frac{d \cos (x+y)}{d(x+y)} \times \frac{d(x+y)}{d x}=0$ [Using chain rule]
$\cos (x y) \times\left[x \frac{d y}{d x}+y \frac{d x}{d x}\right]+(-\sin (x+y))\left[\frac{d x}{d x}+\frac{d y}{d x}\right]=0$ $\left[\begin{array}{c} \frac{d(\sin x)}{d x}=\cos x \\ \frac{d(\cos x)}{d x}=-\sin x \\ \frac{d(u v)}{d x}=u \cdot \frac{d v}{d x}+v \cdot \frac{d u}{d x} \end{array}\right]$$\cos x y\left[x \frac{d y}{d x}+y\right]+(-\sin (x+y))\left[1+\frac{d y}{d x}\right]=0$$x \cos x y \cdot \frac{d y}{d x}+y \cos x y-\sin (x+y)-\sin (x+y) \frac{d y}{d x}=0$$\frac{d y}{d x}(x \cos x y-\sin (x+y))=\sin (x+y)-y \cos x y$$\frac{d y}{d x}=\frac{\sin (x+y)-y \cos x y}{x \cos x y-\sin (x+y)}$Hence,
$\frac{d y}{d x}=\frac{\sin (x+y)-y \cos x y}{x \cos x y-\sin (x+y)}$ is the required answer.
Differentiation exercise 10.4 question 12
Answer:
$\sqrt{\frac{1-y^{2}}{1-x^{2}}}$Hint:
Use
$(\sin A-\sin B) \text { and }(\cos A+\cos B)$ to formulas and use
$\frac{d\left(\sin ^{-1} x\right)}{d x}=\frac{1}{\sqrt{1-x^{2}}}$Given:
$\sqrt{1-x^{2}}+\sqrt{1-y^{2}}=a(x-y)$Solution:
Let
$x=\sin A, y=\sin B$So, the equation will become
$\sqrt{1-\sin ^{2} A}+\sqrt{1-\sin ^{2} B}=a(\sin A-\sin B)$$\sqrt{\cos ^{2} A}+\sqrt{\cos ^{2} B}=a(\sin A-\sin B) \quad\left[\because \sin ^{2} \theta+\cos ^{2} \theta=1\right]$$\begin{aligned} &\cos A+\cos B=a(\sin A-\sin B) \\ &a=\frac{\cos A+\cos B}{\sin A-\sin B} \end{aligned}$$a=\frac{2 \cos \left(\frac{A+B}{2}\right) \cdot \cos \left(\frac{A-B}{2}\right)}{2 \cos \left(\frac{A+B}{2}\right) \cdot \sin \left(\frac{A-B}{2}\right)}$ $\left[\begin{array}{l} \sin A-\sin B=2 \cos \left(\frac{A+B}{2}\right) \cdot \sin \left(\frac{A-B}{2}\right) \\\\ \cos A+\cos B=2 \cos \left(\frac{A+B}{2}\right) \cdot \cos \left(\frac{A-B}{2}\right) \end{array}\right]$$a=\cot \left(\frac{A-B}{2}\right)$$\begin{aligned} &\cot ^{-1} a=\frac{A-B}{2} \\ &2 \cot ^{-1} a=A-B \end{aligned}$ $\left[\because \frac{\cos \theta}{\sin \theta}=\cot \theta\right]$$2 \cot ^{-1} a=\sin ^{-1} x-\sin ^{-1} y \quad[x=\sin A, y=\sin B]$Differentiate the above equation w.r.t x
$\frac{d\left(2 \cot ^{-1} a\right)}{d x}=\frac{d\left(\sin ^{-1} x-\sin ^{-1} y\right)}{d x}$$2 \frac{d\left(\cot ^{-1} a\right)}{d x}=\frac{d\left(\sin ^{-1} x\right)}{d x}-\frac{d\left(\sin ^{-1} y\right)}{d x}$$2 \times 0=\frac{1}{\sqrt{1-x^{2}}}-\frac{d\left(\sin ^{-1} y\right)}{d y} \times \frac{d y}{d x}$ $\left[\because \frac{d\left(\sin ^{-1} x\right)}{d x}=\frac{1}{\sqrt{1-x^{2}}}, \frac{d(\operatorname{cons} \tan t)}{d x}=0\right]$$0=\frac{1}{\sqrt{1-x^{2}}}-\frac{1}{\sqrt{1-y^{2}}} \cdot \frac{d y}{d x}$$\frac{1}{\sqrt{1-y^{2}}} \cdot \frac{d y}{d x}=\frac{1}{\sqrt{1-x^{2}}}$$\frac{d y}{d x}=\frac{\sqrt{1-y^{2}}}{\sqrt{1-x^{2}}}$Hence, if
$\sqrt{1-x^{2}}+\sqrt{1-y^{2}}=a(x-y)$Then,
$\frac{d y}{d x}=\frac{\sqrt{1-y^{2}}}{\sqrt{1-x^{2}}}$ is the required answer
Hence proved
Differentiation exercise 10.4 question 13
Answer:
$-\sqrt{\frac{1-y^{2}}{1-x^{2}}}$Hint:
Use trigonometric identities and differentiation formula of inverse trigonometric functions
Given:
$y \sqrt{1-x^{2}}+x \sqrt{1-y^{2}}=1$Solution:
Let
$x=\sin A, y=\sin B$$\therefore$ The given equation becomes
$\sin B \sqrt{1-\sin ^{2} A}+\sin A \sqrt{1-\sin ^{2} B}=1$$\sin B \sqrt{\cos ^{2} A}+\sin A \sqrt{\cos ^{2} B}=1 \quad\left[\because \sin ^{2} \theta+\cos ^{2} \theta=1\right]$$\sin B \cos A+\sin A \cos B=1$$\sin (A+B)=1 \quad[\because \sin (A+B)=\sin A \cos B+\cos A \sin B]$$\begin{aligned} &A+B=\sin ^{-1}(1) \\ &A+B=\frac{\pi}{2} \end{aligned}$$\therefore \sin ^{-1} x+\sin ^{-1} y=\frac{\pi}{2} \quad[\because x=\sin A, y=\sin B]$Differentiate
$\left(\sin ^{-1} x+\sin ^{-1} y=\frac{\pi}{2}\right)$ w.r.t x
$\frac{d\left(\sin ^{-1} x+\sin ^{-1} y\right)}{d x}=\frac{d\left(\frac{\pi}{2}\right)}{d x}$$\frac{d\left(\sin ^{-1} x\right)}{d x}+\frac{d\left(\sin ^{-1} y\right)}{d x}=0 \quad\left[\because \frac{d(\operatorname{cons} \tan t)}{d x}=0\right]$$\frac{1}{\sqrt{1-x^{2}}}+\frac{d\left(\sin ^{-1} y\right)}{d y} \times \frac{d y}{d x}=0 \quad\left[\because \frac{d\left(\sin ^{-1} x\right)}{d x}=\frac{1}{\sqrt{1-x^{2}}}\right]$$\frac{1}{\sqrt{1-x^{2}}}+\frac{1}{\sqrt{1-y^{2}}} \cdot \frac{d y}{d x}=0$$\frac{1}{\sqrt{1-y^{2}}} \cdot \frac{d y}{d x}=-\frac{1}{\sqrt{1-x^{2}}}$$\frac{d y}{d x}=\frac{-\sqrt{1-y^{2}}}{\sqrt{1-x^{2}}}$$\frac{d y}{d x}=-\sqrt{\frac{1-y^{2}}{1-x^{2}}}$Hence if
$y \sqrt{1-x^{2}}+x \sqrt{1-y^{2}}=1$Then,
$\frac{d y}{d x}=-\sqrt{\frac{1-y^{2}}{1-x^{2}}}$ Is the required answer
Differentiation exercise 10.4 question 14
Answer:
$\frac{d y}{d x}+y^{2}=0$Hint:
Use product rule
Given:
$x y=1$Solution:
Differentiate
$x y=1$ w.r.t x
$\frac{d(x y)}{d x}=\frac{d(1)}{d x}$$x \frac{d y}{d x}+y \frac{d x}{d x}=0$ $\left[\begin{array}{l} \because \frac{d(\operatorname{cons} \tan t)}{d x}=0 \\ \frac{d(u \cdot v)}{d x}=u \cdot \frac{d v}{d x}+v \cdot \frac{d u}{d x} \end{array}\right]$$x \frac{d y}{d x}+y=0$$\begin{aligned} &x \frac{d y}{d x}=-y \\ &\frac{d y}{d x}=-\frac{y}{x} \end{aligned}$$\frac{d y}{d x}=-\frac{y}{\left(\frac{1}{y}\right)} \; \; \; \; \; \; \; \quad\left[\begin{array}{c} x y=1 \\ x=\frac{1}{y} \end{array}\right]$$\frac{d y}{d x}=-y^{2} \; \; \; \; \; \; \; \; \; \; \quad\left[\frac{d y}{d x}+y^{2}=0\right]$Hence, if
$x y=1$Then
$\frac{d y}{d x}+y^{2}=0$ hence proved
Differentiation exercise 10.4 question 15
Answer:
$2 \frac{d y}{d x}+y^{3}=0$Hint:
Use product rule and
$\frac{d\left(x^{n}\right)}{d x}=n x^{n-1}$Given:
$x y^{2}=1$Solution:
Differentiate
$\left[x y^{2}=1\right]$ w.r.t x
$\frac{d\left(x y^{2}\right)}{d x}=\frac{d(1)}{d x}$$x \frac{d y^{2}}{d x}+y^{2} \frac{d x}{d x}=0$ $\left[\because \frac{d(\operatorname{cons} \tan t)}{d x}=0\right]$ [Product rule
$\frac{d(u v)}{d x}=u \cdot \frac{d v}{d x}+v \cdot \frac{d u}{d x}$]
$x \frac{d y^{2}}{d y} \times \frac{d y}{d x}+y^{2}=0$$x(2 y) \times \frac{d y}{d x}+y^{2}=0$ $\left[\because \frac{d\left(x^{n}\right)}{d x}=n x^{n-1}\right]$$2 x y \frac{d y}{d x}+y^{2}=0$$\begin{aligned} &\frac{d y}{d x}=-\frac{y^{2}}{2 x y}=\frac{-y}{2 x} \\ &2 \frac{d y}{d x}=-\frac{y}{x} \end{aligned}$$2 \frac{d y}{d x}=-\frac{y}{\left(\frac{1}{y^{2}}\right)}$ $\left[\begin{array}{c} x y^{2}=1 \\ x=\frac{1}{y^{2}} \end{array}\right]$$2 \frac{d y}{d x}+y^{3}=0$Hence, if
$x y^{2}=1$ then
$2 \frac{d y}{d x}+y^{3}=0$ is the required answer
Hence proved
Differentiation exercise 10.4 question 16
Answer:
$(1+x)^{2} \frac{d y}{d x}+1=0$Hint:
Use quotient rule and algebraic identities
Given:
$x \sqrt{1+y}+y \sqrt{1+x}=0$Solution:
$\begin{aligned} &x \sqrt{1+y}+y \sqrt{1+x}=0 \\ &x \sqrt{1+y}=-y \sqrt{1+x} \end{aligned}$Squaring both the side,
$(x \sqrt{1+y})^{2}=(-y \sqrt{1+x})^{2}$$\begin{aligned} &x^{2}(1+y)=y^{2}(1+x) \\ &x^{2}+x^{2} y=y^{2}+x y^{2} \end{aligned}$$x^{2}-y^{2}=x y^{2}-x^{2} y$$(x+y)(x-y)=x y(y-x)$ $\left[\because a^{2}-b^{2}=(a+b)(a-b)\right]$$\begin{aligned} &(x+y)=-x y \\ &y+x y=-x \\ &y(1+x)=-x \end{aligned}$$y=\frac{-x}{1+x}$Differentiate this above equation w.r.t x
$\frac{d y}{d x}=\frac{d}{d x}\left(\frac{-x}{1+x}\right)$$\frac{d y}{d x}=\frac{(1+x) \cdot \frac{d(-x)}{d x}-(-x) \cdot \frac{d(1+x)}{d x}}{(1+x)^{2}}$ [Using quotient rule]
$\frac{d y}{d x}=\frac{-(1+x)+x(0+1)}{(1+x)^{2}}$ $\left[\because \frac{d\left(x^{n}\right)}{d x}=n x^{n-1}\right]$$\begin{aligned} &\frac{d y}{d x}=\frac{-(1+x)+x}{(1+x)^{2}} \\ &\frac{d y}{d x}=\frac{-1-x+x}{(1+x)^{2}} \end{aligned}$$\frac{d y}{d x}=-\frac{1}{(1+x)^{2}}$$(1+x)^{2} \frac{d y}{d x}=-1$$(1+x)^{2} \frac{d y}{d x}+1=0$Hence proved
Differentiation exercise 10.4 question 17
Answer:
$\frac{d y}{d x}=\frac{x+y}{x-y}$Hint:
Use quotient rule and properties of logarithm
Given:
$\log \sqrt{x^{2}+y^{2}}=\tan ^{-1}\left(\frac{y}{x}\right)$Solution:
$\log \sqrt{x^{2}+y^{2}}=\tan ^{-1}\left(\frac{y}{x}\right)$$\log \left(x^{2}+y^{2}\right)^{\frac{1}{2}}=\tan ^{-1}\left(\frac{y}{x}\right)$$\frac{1}{2} \log \left(x^{2}+y^{2}\right)=\tan ^{-1}\left(\frac{y}{x}\right) \quad\left[\because \log a^{m}=m \log a\right]$Differentiate this above equation w.r.t x
$\frac{1}{2} \cdot \frac{d}{d x}\left(\log \left(x^{2}+y^{2}\right)\right)=\frac{d}{d x}\left(\tan ^{-1}\left(\frac{y}{x}\right)\right)$$\frac{1}{2} \cdot \frac{d \log \left(x^{2}+y^{2}\right)}{d\left(x^{2}+y^{2}\right)} \times\left(\frac{d x^{2}}{d x}+\frac{d y^{2}}{d x}\right)=\frac{1}{1+\left(\frac{y}{x}\right)^{2}} \times \frac{x \frac{d y}{d x}-y \frac{d x}{d x}}{x^{2}}$$\left[\because \frac{d \log x}{d x}=\frac{1}{x}, \frac{d \tan ^{-1} x}{d x}=\frac{1}{1+x^{2}}, \frac{d}{d x}\left(\frac{u}{v}\right)=\frac{v \frac{d u}{d x}-u \frac{d v}{d x}}{v^{2}}\right]$$\frac{1}{2} \times\left(\frac{1}{x^{2}+y^{2}}\right) \times\left(2 x+\frac{d y^{2}}{d y} \times \frac{d y}{d x}\right)=\frac{1}{1+\left(\frac{y^{2}}{x^{2}}\right)} \times \frac{x \frac{d y}{d x}-y}{x^{2}}$$\begin{aligned} &\text { - }\\ &\frac{1}{2\left(x^{2}+y^{2}\right)} \times\left(2 x+2 y \frac{d y}{d x}\right)=\frac{1}{\left(\frac{x^{2}+y^{2}}{x^{2}}\right)} \cdot\left(\frac{x}{x^{2}} \cdot \frac{d y}{d x}-\frac{y}{x^{2}}\right) \end{aligned}$$\frac{1}{2\left(x^{2}+y^{2}\right)} \times 2\left(x+y \frac{d y}{d x}\right)=\frac{x^{2}}{x^{2}+y^{2}} \times\left(\frac{1}{x} \cdot \frac{d y}{d x}-\frac{y}{x^{2}}\right)$$\frac{x}{x^{2}+y^{2}}+\frac{y}{x^{2}+y^{2}} \cdot \frac{d y}{d x}=\left[\frac{x^{2}}{x^{2}+y^{2}} \times \frac{1}{x} \cdot \frac{d y}{d x}\right]-\frac{x^{2}}{x^{2}+y^{2}} \times \frac{y}{x^{2}}$$\frac{x}{x^{2}+y^{2}}+\frac{y}{x^{2}+y^{2}} \cdot \frac{d y}{d x}=\left[\frac{x}{x^{2}+y^{2}} \cdot \frac{d y}{d x}\right]-\frac{y}{x^{2}+y^{2}}$$\frac{x}{x^{2}+y^{2}} \cdot \frac{d y}{d x}-\frac{y}{x^{2}+y^{2}} \cdot \frac{d y}{d x}=\frac{x}{x^{2}+y^{2}}+\frac{y}{x^{2}+y^{2}}$$\frac{d y}{d x}\left(\frac{x-y}{x^{2}+y^{2}}\right)=\frac{x+y}{\left(x^{2}+y^{2}\right)}$$\frac{d y}{d x}=\frac{x+y}{x-y}$Hence proved
Differentiation exercise 10.4 question 18
Answer:
$\frac{d y}{d x}=\frac{y}{x}$Hint:
Use quotient rule
Given:
$\sec \left(\frac{x+y}{x-y}\right)=a$Solution:
$\begin{aligned} &\sec \left(\frac{x+y}{x-y}\right)=a \\ &\sec ^{-1} a=\frac{x+y}{x-y} \end{aligned}$Differentiating
$\left[\sec ^{-1} a=\frac{x+y}{x-y}\right]$ w.r.t x
$\frac{d\left(\sec ^{-1} a\right)}{d x}=\frac{d}{d x}\left(\frac{x+y}{x-y}\right)$$0=\frac{(x-y) \frac{d(x+y)}{d x}-(x+y) \frac{d(x-y)}{d x}}{(x-y)^{2}}$ [Use quotient rule]
$\frac{(x-y)\left(\frac{d x}{d x}+\frac{d y}{d x}\right)-(x+y)\left(\frac{d x}{d x}-\frac{d y}{d x}\right)}{(x-y)^{2}}=0$$(x-y)\left(1+\frac{d y}{d x}\right)-(x+y)\left(1-\frac{d y}{d x}\right)=0$$(x-y)+(x-y) \frac{d y}{d x}-(x+y)+(x+y) \frac{d y}{d x}=0$$\frac{d y}{d x}[(x-y)+(x+y)]=x+y-(x-y)$$\frac{d y}{d x}[x-y+x+y]=x+y-x+y$$\frac{d y}{d x}(2 x)=2 y$$\begin{aligned} &\frac{d y}{d x}=\frac{2 y}{2 x}=\frac{y}{x} \\ &\frac{d y}{d x}=\frac{y}{x} \end{aligned}$Thus, proved
Differentiation exercise 10.4 question 19
Answer:
$\frac{d y}{d x}=\frac{x}{y}\left(\frac{1-\tan a}{1+\tan a}\right)$Hint:
Use differentiation formulas
Given:
$\tan ^{-1}\left(\frac{x^{2}-y^{2}}{x^{2}+y^{2}}\right)=a$Solution:
$\tan ^{-1}\left(\frac{x^{2}-y^{2}}{x^{2}+y^{2}}\right)=a$$\tan a=\frac{x^{2}-y^{2}}{x^{2}+y^{2}}$$\begin{aligned} &\left(x^{2}+y^{2}\right) \tan a=x^{2}-y^{2} \\ &x^{2}-y^{2}=(\tan a)\left(x^{2}+y^{2}\right) \end{aligned}$Differentiate the given equation w.r.t x
$\frac{d}{d x}\left(x^{2}-y^{2}\right)=\tan a \cdot \frac{d}{d x}\left(x^{2}+y^{2}\right)$$\frac{d\left(x^{2}\right)}{d x}-\frac{d y^{2}}{d x}=\tan a \cdot\left[\frac{d x^{2}}{d x}+\frac{d y^{2}}{d x}\right]$$2 x-\frac{d y^{2}}{d y} \times \frac{d y}{d x}=\tan a \cdot\left[2 x+\frac{d y^{2}}{d y} \times \frac{d y}{d x}\right]$$2 x-2 y \frac{d y}{d x}=\tan a\left[2 x+2 y \cdot \frac{d y}{d x}\right]$$2 x-2 y \frac{d y}{d x}=2 x \tan a+2 y \tan a \frac{d y}{d x}$$2 y \tan a \frac{d y}{d x}+2 y \frac{d y}{d x}=2 x-2 x \tan a$$2 y \frac{d y}{d x}(\tan a+1)=2 x(1-\tan a)$$\frac{d y}{d x}=\frac{(1-\tan a)}{(1+\tan a)} \times \frac{2 x}{2 y}$$\frac{d y}{d x}=\left(\frac{1-\tan a}{1+\tan a}\right) \times \frac{x}{y}$Thus, proved
Differentiation exercise 10.4 question 20
Answer:
$\frac{d y}{d x}=-\frac{y\left(x^{2} y+x+y\right)}{x\left(x y^{2}+x+y\right)}$Hint:
Use product rule and chain rule
Given:
$x y \log (x+y)=1$Solution:
$x y \log (x+y)=1$Differentiate the given equation w.r.t x
$\frac{d}{d x}[x y \log (x+y)]=\frac{d(1)}{d x}$$x y \cdot \frac{d}{d x}(\log (x+y))+\log (x+y) \frac{d(x y)}{d x}=0$ $\left[\because \frac{d(\operatorname{cons} \tan t)}{d x}=0\right]$$x y\left[\frac{d \log (x+y)}{d(x+y)} \times \frac{d(x+y)}{d x}\right]+\log (x+y)\left[x \frac{d y}{d x}+y \frac{d x}{d x}\right]=0$ [Use product rule and chain rule]
$x y\left[\frac{1}{x+y} \times\left(\frac{d x}{d x}+\frac{d y}{d x}\right)\right]+\log (x+y)\left[x \frac{d y}{d x}+y\right]=0$$x y\left[\frac{1}{x+y}+\frac{1}{x+y} \frac{d y}{d x}\right]+x \log (x+y) \frac{d y}{d x}+y \log (x+y)=0$$\frac{x y}{x+y}+\frac{x y}{x+y} \frac{d y}{d x}+x \log (x+y) \frac{d y}{d x}+y \log (x+y)=0$$\frac{d y}{d x}\left[\frac{x y}{x+y}+x \log (x+y)\right]=-\frac{x y}{x+y}-y \log (x+y)$Also
$x y \log (x+y)=1$ $\left[\log (x+y)=\frac{1}{x y}\right]$Put
$\log (x+y)=\frac{1}{x y}$ in the above equation
$\frac{d y}{d x}\left[\frac{x y}{x+y}+x \cdot \frac{1}{x y}\right]=-\frac{x y}{x+y}-y \cdot \frac{1}{x y}$$\frac{d y}{d x}\left[\frac{x y}{x+y}+\frac{1}{y}\right]=-\left(\frac{x y}{x+y}+\frac{1}{x}\right)$$\frac{d y}{d x}\left[\frac{x y^{2}+(x+y)}{y(x+y)}\right]=-\left(\frac{x^{2} y+(x+y)}{x(x+y)}\right)$$\frac{d y}{d x}\left[\frac{\left(x y^{2}+(x+y)\right)}{y}\right]=-\left[\frac{\left(x^{2} y+(x+y)\right)}{x}\right]$$\begin{aligned} &\frac{d y}{d x}=\frac{-\left(x^{2} y+x+y\right)}{\left(x y^{2}+x+y\right)} \times \frac{y}{x} \\ &\frac{d y}{d x}=\frac{-y}{x} \cdot\left(\frac{x^{2} y+x+y}{x y^{2}+x+y}\right) \end{aligned}$Thus, proved
Differentiation exercise 10.4 question 21
Answer:
$\frac{d y}{d x}=\frac{\sin ^{2}(a+y)}{\sin (a+y)-y \cos (a+y)}$Hint:
Use chain rule
Given:
$y=x \sin (a+y)$Solution:
$y=x \sin (a+y)$Differentiate the given equation w.r.t x
$\frac{d y}{d x}=\frac{d(x \sin (a+y))}{d x}$$\frac{d y}{d x}=x \cdot \frac{d \sin (a+y)}{d x}+\sin (a+y) \cdot \frac{d x}{d x}$$\frac{d y}{d x}=x\left[\frac{d \sin (a+y)}{d(a+y)} \times \frac{d(a+y)}{d y} \times \frac{d y}{d x}\right]+\sin (a+y)$ [Using chain rule]
$=x\left[\cos (a+y) \times\left(\frac{d a}{d y}+\frac{d y}{d y}\right) \times \frac{d y}{d x}\right]+\sin (a+y)$$=x\left[\cos (a+y) \times(0+1) \times \frac{d y}{d x}\right]+\sin (a+y)$$\frac{d y}{d x}=x \cos (a+y) \frac{d y}{d x}+\sin (a+y)$$\frac{d y}{d x}-x \cos (a+y) \frac{d y}{d x}=\sin (a+y)$$\frac{d y}{d x}(1-x \cos (a+y))=\sin (a+y)$$\frac{d y}{d x}=\frac{\sin (a+y)}{1-x \cos (a+y)}$$y=x \sin (a+y)$$x=\frac{y}{\sin (a+y)}$Put
$x=\frac{y}{\sin (a+y)}$ in the above equation
$\frac{d y}{d x}=\frac{\sin (a+y)}{1-\frac{y}{\sin (a+y)} \times \cos (a+y)}$$\frac{d y}{d x}=\frac{\sin (a+y)}{\left[\frac{\sin (a+y)-y \cos (a+y)}{\sin (a+y)}\right]}$$\frac{d y}{d x}=\frac{\sin ^{2}(a+y)}{\sin (a+y)-y \cos (a+y)}$Thus, proved
Differentiation exercise 10.4 question 22
Answer:
$\frac{d y}{d x}=\frac{\sin ^{2}(a+y)}{\sin a}$Hint:
Use chain rule
Given:
$x \sin (a+y)+\sin a \cos (a+y)=0$Solution:
$\begin{aligned} &x \sin (a+y)+\sin a \cos (a+y)=0 \\ &x \sin (a+y)=-\sin a \cos (a+y) \end{aligned}$$-\frac{x}{\sin a}=\frac{\cos (a+y)}{\sin (a+y)}$$-\frac{x}{\sin a}=\cot (a+y)$Differentiating equation w.r.t x
$\frac{d}{d x}\left(\frac{-x}{\sin a}\right)=\frac{d}{d x} \cot (a+y)$$\frac{-1}{\sin a} \cdot \frac{d x}{d x}=\frac{d \cot (a+y)}{d(a+y)} \times \frac{d(a+y)}{d x}$ [Use chain rule]
$\frac{-1}{\sin a}=-\cos e c^{2}(a+y) \times\left(\frac{d a}{d x}+\frac{d y}{d x}\right)$ $\left[\because \frac{d(\cot \theta)}{d \theta}=-\cos e c^{2} \theta\right]$$-\frac{1}{\sin a}=-\cos e c^{2}(a+y)\left[0+\frac{d y}{d x}\right]$$-\frac{1}{\sin a}=-\operatorname{cosec}^{2}(a+y) \cdot \frac{d y}{d x}$$\frac{d y}{d x}=\frac{1}{\sin a \cdot \cos e c^{2}(a+y)}$$\frac{d y}{d x}=\frac{1}{\sin a \cdot\left(\frac{1}{\sin ^{2}(a+y)}\right)}$ $\left[\because \cos e c \theta=\frac{1}{\sin \theta}\right]$$\frac{d y}{d x}=\frac{\sin ^{2}(a+y)}{\sin a}$Thus, proved
Differentiation exercise 10.4 question 23
Answer:
$\frac{d y}{d x}=\frac{\sin y}{1-x \cos y}$Hint:
Use product rule and chain rule
Given:
$y=x \sin y$Solution:
$y=x \sin y$Differentiate w.r.t x
$\frac{d y}{d x}=\frac{d(x \sin y)}{d x}$$\frac{d y}{d x}=x \cdot \frac{d(\sin y)}{d x}+\sin y \cdot \frac{d x}{d x}$ [Using product rule]
$\frac{d y}{d x}=x \cdot \frac{d \sin y}{d y} \cdot \frac{d y}{d x}+\sin y$ [Using chain rule]
$\frac{d y}{d x}=x \cdot \cos y \cdot \frac{d y}{d x}+\sin y$$\frac{d y}{d x}-x \cos y \frac{d y}{d x}=\sin y$$\frac{d y}{d x}(1-x \cos y)=\sin y$$\frac{d y}{d x}=\frac{\sin y}{1-x \cos y}$Thus, proved
Differentiation exercise 10.4 question 24
Answer:
$\left(x^{2}+1\right) \frac{d y}{d x}+x y+1=0$Hint:
Use product rule and chain rule
Given:
$y \sqrt{x^{2}+1}=\log \left(\sqrt{x^{2}+1}-x\right)$Solution:
$y \sqrt{x^{2}+1}=\log \left(\sqrt{x^{2}+1}-x\right)$Differentiate w.r.t x
$\frac{d}{d x}\left(y \sqrt{x^{2}+1}\right)=\frac{d}{d x}\left(\log \left(\sqrt{x^{2}+1}-x\right)\right)$$y \frac{d}{d x}\left(\sqrt{x^{2}+1}\right)+\left(\sqrt{x^{2}+1}\right) \frac{d y}{d x}=\frac{d\left(\log \left(\sqrt{x^{2}+1}-x\right)\right)}{d\left(\sqrt{x^{2}+1}-x\right)} \times \frac{d\left(\sqrt{x^{2}+1}-x\right)}{d x}$[Use product rule and chain rule]
$\Rightarrow y \cdot\left[\frac{d\left(\sqrt{x^{2}+1}\right)}{d\left(x^{2}+1\right)} \times \frac{d\left(x^{2}+1\right)}{d x}\right]+\sqrt{x^{2}+1} \frac{d y}{d x}=\frac{1}{\left(\sqrt{x^{2}+1}-x\right)} \times\left(\frac{\left(\sqrt{x^{2}+1}\right)}{d x}-\frac{d x}{d x}\right)$$y \cdot \frac{1}{2 \sqrt{x^{2}+1}} \cdot 2 x+\sqrt{x^{2}+1} \frac{d y}{d x}=\frac{1}{\left(\sqrt{x^{2}+1}-x\right)} \times\left[\frac{d \sqrt{x^{2}+1}}{d\left(x^{2}+1\right)} \times \frac{d\left(x^{2}+1\right)}{d x}-1\right]$$\frac{x y}{\sqrt{x^{2}+1}}+\sqrt{x^{2}+1} \frac{d y}{d x}=\frac{1}{\left(\sqrt{x^{2}+1}-x\right)} \cdot\left[\frac{1}{2 \sqrt{x^{2}+1}} \times 2 x-1\right]$$\frac{x y}{\sqrt{x^{2}+1}}+\sqrt{x^{2}+1} \cdot \frac{d y}{d x}=\frac{1}{\left(\sqrt{x^{2}+1}-x\right)} \cdot\left[\frac{x-\sqrt{x^{2}+1}}{\sqrt{x^{2}+1}}\right]$$\frac{x y}{\sqrt{x^{2}+1}}+\sqrt{x^{2}+1} \cdot \frac{d y}{d x}=-\frac{1}{\sqrt{x^{2}+1}}$$\sqrt{x^{2}+1} \cdot \frac{d y}{d x}=\frac{-1}{\sqrt{x^{2}+1}}-\frac{x y}{\sqrt{x^{2}+1}}$$\sqrt{x^{2}+1} \cdot \frac{d y}{d x}=\frac{-1-x y}{\sqrt{x^{2}+1}}$$\left(x^{2}+1\right) \frac{d y}{d x}=-(1+x y)$$\left(x^{2}+1\right) \frac{d y}{d x}+1+x y=0$Thus, proved
Differentiation exercise 10.4 question 25
Answer:
$\frac{d y}{d x}=\frac{2 x^{3}+y-x^{2} y \cos x y}{x\left(x^{2} \cos x y+1+2 x y\right)}$Hint:
Use chain rule and
$\frac{d\left(x^{n}\right)}{d x}=n x^{n-1}$Given:
$\sin (x y)+\frac{y}{x}=x^{2}-y^{2}$Solution:
$\sin (x y)+\frac{y}{x}=x^{2}-y^{2}$Differentiate w.r.t x
$\frac{d}{d x}(\sin x y)+\frac{d}{d x}\left(\frac{y}{x}\right)=\frac{d\left(x^{2}\right)}{d x}-\frac{d\left(y^{2}\right)}{d x}$$\frac{d(\sin x y)}{d(x y)} \times \frac{d(x y)}{d x}+\frac{d}{d x}\left(\frac{y}{x}\right)=2 x-\frac{d y^{2}}{d y} \times \frac{d y}{d x}$ [Using chain rule and
$\frac{d\left(x^{n}\right)}{d x}=n x^{n-1}$]
$\cos x y \times\left(x \frac{d y}{d x}+y \frac{d x}{d x}\right)+\frac{x \frac{d y}{d x}-y \frac{d x}{d x}}{x^{2}}=2 x-2 y \frac{d y}{d x}$$x \cos x y \frac{d y}{d x}+y \cos x y+\frac{x \frac{d y}{d x}-y}{x^{2}}=2 x-2 y \frac{d y}{d x}$$x \cos x y \frac{d y}{d x}+y \cos x y+\frac{1}{x} \frac{d y}{d x}-\frac{y}{x^{2}}=2 x-2 y \frac{d y}{d x}$$x \cos x y \frac{d y}{d x}+\frac{1}{x} \frac{d y}{d x}+2 y \frac{d y}{d x}=2 x+\frac{y}{x^{2}}-y \cos x y$$\frac{d y}{d x}\left(x \cos x y+\frac{1}{x}+2 y\right)=2 x+\frac{y}{x^{2}}-y \cos x y$$\frac{d y}{d x}\left(\frac{x^{2} \cos x y+1+2 x y}{x}\right)=\frac{2 x^{3}+y-x^{2} y \cos x y}{x^{2}}$$\frac{d y}{d x}\left(x^{2} \cos x y+2 x y+1\right)=\frac{1}{x}\left(2 x^{3}+y-x^{2} y \cos x y\right)$$\frac{d y}{d x}=\frac{2 x^{3}+y-x^{2} y \cos x y}{x\left(x^{2} \cos x y+1+2 x y\right)}$Hence proved
Differentiation exercise 10.4 question 26
Answer:
$\frac{d y}{d x}=\frac{\sec ^{2}(x+y)+\sec ^{2}(x-y)}{\sec ^{2}(x-y)-\sec ^{2}(x+y)}$Hint:
Use chain rule
Given:
$\tan (x+y)+\tan (x-y)=1$Solution:
$\tan (x+y)+\tan (x-y)=1$Differentiate w.r.t x
$\frac{d(\tan (x+y))}{d x}+\frac{d(\tan (x-y))}{d x}=\frac{d(1)}{d x}$$\frac{d(\tan x+y)}{d(x+y)} \times \frac{d(x+y)}{d x}+\frac{d(\tan (x-y))}{d(x-y)} \times \frac{d(x-y)}{d x}=0$[Using chain rule and
$\frac{d(\operatorname{cons} \tan t)}{d x}=0$]$\sec ^{2}(x+y) \times\left(\frac{d x}{d x}+\frac{d y}{d x}\right)+\sec ^{2}(x-y)\left(\frac{d x}{d x}-\frac{d y}{d x}\right)=0$$\sec ^{2}(x+y)+\sec ^{2}(x+y) \frac{d y}{d x}+\sec ^{2}(x-y)-\sec ^{2}(x-y) \frac{d y}{d x}=0$$\frac{d y}{d x}\left(\sec ^{2}(x+y)-\sec ^{2}(x-y)\right)=-\left(\sec ^{2}(x+y)+\sec ^{2}(x-y)\right)$$\frac{d y}{d x}=\frac{\sec ^{2}(x+y)+\sec ^{2}(x-y)}{\sec ^{2}(x-y)-\sec ^{2}(x+y)}$Differentiation exercise 10.4 question 27
Answer:
$\frac{d y}{d x}=\frac{-e^{x}\left(e^{y}-1\right)}{e^{y}\left(e^{x}-1\right)}$Hint:
Use chain rule
Given:
$e^{x}+e^{y}=e^{x+y}$Solution:
$e^{x}+e^{y}=e^{x+y}$Differentiate w.r.t x
$\frac{d}{d x}\left(e^{x}+e^{y}\right)=\frac{d\left(e^{x+y}\right)}{d x}$$\frac{d\left(e^{x}\right)}{d x}+\frac{d\left(e^{y}\right)}{d x}=\frac{d\left(e^{x+y}\right)}{d(x+y)} \times \frac{d(x+y)}{d x}$ [Using chain rule]
$e^{x}+\frac{d\left(e^{y}\right)}{d y} \times \frac{d y}{d x}=e^{x+y} \times\left(\frac{d x}{d x}+\frac{d y}{d x}\right)$ $\left[\because \frac{d\left(e^{x}\right)}{d x}=e^{x}\right]$$e^{x}+e^{y} \frac{d y}{d x}=e^{x+y}+e^{x+y} \frac{d y}{d x}$$e^{y} \frac{d y}{d x}-e^{x+y} \frac{d y}{d x}=e^{x+y}-e^{x}$$\frac{d y}{d x}\left(e^{y}-e^{x+y}\right)=\left(e^{x+y}-e^{x}\right)$$\frac{d y}{d x}=\frac{e^{x+y}-e^{x}}{e^{y}-e^{x+y}}$$\frac{d y}{d x}=\frac{e^{x} \cdot e^{y}-e^{x}}{e^{y}-e^{x} \cdot e^{y}}$$=\frac{e^{x}\left(e^{y}-1\right)}{e^{y}\left(1-e^{x}\right)}$$=\frac{e^{x}\left(e^{y}-1\right)}{e^{y}\left(-\left(e^{x}-1\right)\right)}$$\frac{d y}{d x}=-\frac{e^{x}\left(e^{y}-1\right)}{e^{y}\left(e^{x}-1\right)}$Thus proved
Differentiation exercise 10.4 question 28
Answer:
$\frac{d y}{d x}=\frac{\cos ^{2}(a+y)}{\sin a}$Hint:
Use chain rule and product rule
Given:
$\cos y=x \cos (a+y)$Solution:
Differentiate the given equation w.r.t x
$\frac{d \cos y}{d x}=\frac{d(x \cos (a+y))}{d x}$$\frac{d(\cos y)}{d y} \times \frac{d y}{d x}=x \frac{d(\cos (a+y))}{d x}+\cos (a+y) \cdot \frac{d x}{d x}$ [Use chain rule and product rule]
$(-\sin y) \times \frac{d y}{d x}=x \times\left[\frac{d \cos (a+y)}{d(a+y)} \times \frac{d(a+y)}{d x}\right]+\cos (a+y)$$-\sin y \frac{d y}{d x}=x \cdot\left(-\sin (a+y) \times\left(\frac{d a}{d x}+\frac{d y}{d x}\right)\right)+\cos (a+y)$$-\sin y \frac{d y}{d x}=-x \sin (a+y)\left(0+\frac{d y}{d x}\right)+\cos (a+y)$ $\left[\because \frac{d(\operatorname{cons} \tan t)}{d x}=0\right]$$-\sin y \frac{d y}{d x}=-x \sin (a+y) \frac{d y}{d x}+\cos (a+y)$$x \sin (a+y) \frac{d y}{d x}-\sin y \frac{d y}{d x}=\cos (a+y)$$\frac{d y}{d x}(x \sin (a+y)-\sin y)=\cos (a+y)$Also
$\cos y=x \cos (a+y)$$x=\frac{\cos y}{\cos (a+y)}$Put this values of x in the above equation
$\frac{d y}{d x}\left[\frac{\cos y}{\cos (a+y)} \sin (a+y)-\sin y\right]=\cos (a+y)$$\frac{d y}{d x}\left[\frac{\cos y \cdot \sin (a+y)-\sin y \cdot \cos (a+y)}{\cos (a+y)}\right]=\cos (a+y)$$\frac{d y}{d x}\left[\frac{\sin ((a+y)-y)}{\cos (a+y)}\right]=\cos (a+y)$ $[\because \sin (A-B)=\sin A \cos B-\cos A \sin B]$$\frac{d y}{d x} \times\left[\frac{\sin a}{\cos (a+y)}\right]=\cos (a+y)$$\begin{aligned} &\frac{d y}{d x}=\frac{\cos ^{2}(a+y)}{\sin a} \end{aligned}$Thus, proved
Differentiation exercise 10.4 question 29
Answer:
$\frac{d y}{d x}=\frac{\pi}{4}(\sqrt{2}+1)$Hint:
Use chain rule and product rule
Given:
$\sin ^{2} y+\cos x y=K$Solution:
$\sin ^{2} y+\cos x y=K$Differentiate the given equation w.r.t x
$\frac{d}{d x}\left(\sin ^{2} y+\cos x y\right)=\frac{d(k)}{d x}$$\frac{d \sin ^{2} y}{d x}+\frac{d \cos x y}{d x}=0$ $\left[\because \frac{d(\operatorname{con} s \tan t)}{d x}=0\right]$$\left(\frac{d \sin ^{2} y}{d \sin y} \times \frac{d \sin y}{d y} \times \frac{d y}{d x}\right)+\left(\frac{d \cos x y}{d x y}\right) \times \frac{d x y}{d x}=0$ [Using chain rule]
$2 \sin y \times \cos y \times \frac{d y}{d x}+(-\sin x y) \times\left[x \frac{d y}{d x}+y \frac{d x}{d x}\right]=0$ [Using product rule]
$\sin 2 y \frac{d y}{d x}-\sin x y\left(x \frac{d y}{d x}\right)-y \sin x y=0$$\frac{d y}{d x}(\sin 2 y-x \sin x y)=y \sin x y$$\frac{d y}{d x}=\frac{y \sin x y}{\sin 2 y-x \sin x y}$At $x=1, y=\frac{\pi}{4}$$\frac{d y}{d x}=\frac{\left(\frac{\pi}{4}\right) \sin \left(1 \times \frac{\pi}{4}\right)}{\sin \left(2 \times \frac{\pi}{4}\right)-1 \times \sin \left(1 \times \frac{\pi}{4}\right)}$$=\frac{\frac{\pi}{4} \cdot\left(\frac{1}{\sqrt{2}}\right)}{\sin \frac{\pi}{2}-\frac{1}{\sqrt{2}}}$ $\left[\because \sin \frac{\pi}{4}=\frac{1}{\sqrt{2}}, \sin \frac{\pi}{2}=1\right]$$=\frac{\frac{\pi}{4 \sqrt{2}}}{1-\frac{1}{\sqrt{2}}}$$=\frac{\frac{\pi}{4 \sqrt{2}}}{\frac{(\sqrt{2}-1)}{\sqrt{2}}}$$=\frac{\pi \times \sqrt{2}}{(\sqrt{2}-1) 4 \sqrt{2}}=\frac{\pi}{4(\sqrt{2}-1)} \times \frac{\sqrt{2}+1}{\sqrt{2}+1}=\frac{\pi(\sqrt{2}+1)}{4}$Hence at
$x=1, y=\frac{\pi}{4}$$\frac{d y}{d x}=\frac{\pi}{4}(\sqrt{2}+1)$Differentiation exercise 10.4 question 30
Answer:
$\frac{d y}{d x}=8\left[\frac{4}{16+\pi^{2}}-\frac{1}{\log 2}\right]_{\mathrm{At}} x=\frac{\pi}{4}$Hint:
Use chain rule and differentiation of inverse trigonometric function
Given:
$y=\left[\log _{\cos x} \sin x\right]\left[\log _{\sin x} \cos x\right]^{-1}+\sin ^{-1}\left(\frac{2 x}{1+x^{2}}\right)$Solution:
$y=\left[\log _{\cos x} \sin x\right]\left[\log _{\sin x} \cos x\right]^{-1}+\sin ^{-1}\left(\frac{2 x}{1+x^{2}}\right)$$y=\left[\log _{\cos x} \sin x\right]\left[\log _{\cos x} \sin x\right]+\sin ^{-1}\left(\frac{2 x}{1+x^{2}}\right)$ $\left[\because \log _{b} a=\left(\log _{a} b\right)^{-1}\right]$$y=\left[\log _{\cos x} \sin x\right]^{2}+\sin ^{-1}\left(\frac{2 x}{1+x^{2}}\right)$$y=\left(\frac{\log \sin x}{\log \cos x}\right)^{2}+\sin ^{-1}\left(\frac{2 x}{1+x^{2}}\right)$ $\left[\because \log _{a} b=\frac{\log b}{\log a}\right]$$y=\left(\frac{\log \sin x}{\log \cos x}\right)^{2}+\sin ^{-1}\left(\frac{2 x}{1+x^{2}}\right)$Differentiate w.r.t x
$\frac{d y}{d x}=\frac{d}{d x}\left(\frac{\log \sin x}{\log \cos x}\right)^{2}+\frac{d}{d x}\left(\sin ^{-1}\left(\frac{2 x}{1+x^{2}}\right)\right)$$=\left[\frac{d\left(\frac{\log \sin x}{\log \cos x}\right)^{2}}{d\left(\frac{\log \sin x}{\log \cos x}\right)} \times \frac{d\left(\frac{\log \sin x}{\log \cos x}\right)}{d x}\right]+\frac{d \sin ^{-1}\left(\frac{2 x}{1+x^{2}}\right)}{d\left(\frac{2 x}{1+x^{2}}\right)} \times \frac{d\left(\frac{2 x}{1+x^{2}}\right)}{d x}$ [Using chain rule]
$\frac{d y}{d x}=2\left(\frac{\log \sin x}{\log \cos x}\right) \times \frac{d}{d x}\left(\frac{\log \sin x}{\log \cos x}\right)+\frac{1}{\sqrt{1-\left(\frac{2 x}{1+x^{2}}\right)^{2}}} \times \frac{d}{d x}\left(\frac{2 x}{1+x^{2}}\right)$$=\frac{2 \log \sin x}{\log \cos x} \times \frac{\log \cos x \cdot \frac{d(\log \sin x)}{d x}-\log \sin x \cdot \frac{d(\log \cos x)}{d x}}{(\log \cos x)^{2}}$$+\frac{1}{\sqrt{1-\frac{4 x^{2}}{\left(1+x^{2}\right)^{2}}}} \times \frac{\left(1+x^{2}\right) \frac{d(2 x)}{d x}-2 x \frac{d\left(1+x^{2}\right)}{d x}}{\left(1+x^{2}\right)^{2}}$$=\frac{2 \log \sin x}{\log \cos x} \times \frac{\log \cos x \cdot \frac{d(\log (\sin x))}{d \sin x} \times \frac{d(\sin x)}{d x}-\log \sin x \cdot \frac{d(\log \cos x)}{d x}}{(\log \cos x)^{2}}$$+\frac{1}{\sqrt{\frac{1+x^{4}+2 x^{2}-4 x^{2}}{\left(1+x^{2}\right)^{2}}}} \times \frac{\left(1+x^{2}\right) \times 2-(2 x)(2 x)}{\left(1+x^{2}\right)^{2}}$$\frac{d y}{d x}=2 \frac{\log \sin x}{\log \cos x} \times \frac{\log \cos x \times \frac{1}{\sin x} \cos x-\log \sin x \cdot \frac{d(\log \cos x)}{d \cos x} \times \frac{d \cos x}{d x}}{(\log (\cos x))^{2}}$$+\frac{1+x^{2}}{\sqrt{\left(1-x^{2}\right)^{2}}} \times\left[\frac{2+2 x^{2}-4 x^{2}}{\left(1+x^{2}\right)^{2}}\right]$$\frac{d y}{d x}=\frac{2 \log \sin x}{\log \cos x} \times \frac{(\log \cos x) \cot x+(\log \sin x) \times \tan x}{(\log \cos x)^{2}}+\frac{1+x^{2}}{1-x^{2}} \times \frac{2-2 x^{2}}{\left(1+x^{2}\right)^{2}}$$\frac{d y}{d x}=\frac{2 \log \sin x}{(\log \cos x)^{3}} \times \frac{[\cot x \times(\log \cos x)+\tan x \times(\log \sin x)]}{1}+\frac{2}{1+x^{2}}$$\frac{d y}{d x}=\frac{2 \log \sin x}{(\log \cos x)^{3}} \times(\cot x \log \cos x+\tan x \log \sin x)+\frac{2}{1+x^{2}}$Put
$x=\frac{\pi}{4}$$\frac{d y}{d x}=2\left(\frac{\log \left(\sin \frac{\pi}{4}\right)}{\left(\log \left(\cos \frac{\pi}{4}\right)\right)^{3}}\right) \times\left(\cot \frac{\pi}{4} \times \log \cos \frac{\pi}{4}+\tan \frac{\pi}{4} \cdot \log \sin \frac{\pi}{4}\right)+\frac{2}{\left[1+\left(\frac{\pi}{4}\right)^{2}\right]}$ $\left[\because \sin \frac{\pi}{4}=\cos \frac{\pi}{4}=\frac{1}{\sqrt{2}}\right] ;\left[\tan \frac{\pi}{4}=\cot \frac{\pi}{4}=1\right]$$\frac{d y}{d x}=2\left[\frac{\log \left(\frac{1}{\sqrt{2}}\right)}{\left(\log \left(\frac{1}{\sqrt{2}}\right)\right)^{3}}\right]\left[1 \times \log \frac{1}{\sqrt{2}}+1 \times \log \frac{1}{\sqrt{2}}\right]+\frac{2}{\left(1+\frac{\pi^{2}}{16}\right)}$$\frac{d y}{d x}=\frac{2}{\left(\log \frac{1}{\sqrt{2}}\right)^{2}}\left[2 \log \frac{1}{\sqrt{2}}\right]+\frac{32}{16+\pi^{2}}$$=\frac{4}{\left(\log \frac{1}{\sqrt{2}}\right)}+\frac{32}{16+\pi^{2}}$$=\frac{4}{\log (2)^{\frac{-1}{2}}}+\frac{32}{16+\pi^{2}}$$=\frac{4}{\frac{-1}{2} \log 2}+\frac{32}{16+\pi^{2}}$$=\frac{-8}{\log 2}+\frac{32}{16+\pi^{2}}$$\therefore\left(\frac{d y}{d x}\right)_{x=\frac{\pi}{4}}=8\left[\frac{4}{16+\pi^{2}}-\frac{1}{\log 2}\right]$Answer:
$\frac{d y}{d x}=\frac{y}{x}-\sqrt{\frac{y^{2}}{x^{2}}-1}$ At
$x=\frac{\pi}{4}$Hint:
Use chain rule
Given:
$\sqrt{y+x}+\sqrt{y-x}=c$Solution:
$\sqrt{y+x}+\sqrt{y-x}=c$Differentiate the given equation w.r.t x
$\frac{d}{d x}(\sqrt{y+x}+\sqrt{y-x})=\frac{d(c)}{d x}$$\frac{d(\sqrt{y+x})}{d x}+\frac{d(\sqrt{y-x})}{d x}=0$ $\left[\because \frac{d(\operatorname{cons} \tan t)}{d x}=0\right]$$\frac{d(\sqrt{y+x})}{d(y+x)} \times \frac{d(y+x)}{d x}+\frac{d(\sqrt{y-x})}{d(y-x)} \times \frac{d(y-x)}{d x}=0$ [Using chain rule]
$\frac{1}{2 \sqrt{y+x}} \times\left(\frac{d y}{d x}+\frac{d x}{d x}\right)+\frac{1}{2 \sqrt{y-x}} \times\left(\frac{d y}{d x}-\frac{d x}{d x}\right)=0$ $\left[\because \frac{d\left(x^{n}\right)}{d x}=n x^{n-1}\right]$$\frac{1}{2 \sqrt{y+x}}\left(\frac{d y}{d x}+1\right)+\frac{1}{2 \sqrt{y-x}}\left(\frac{d y}{d x}-1\right)=0$$\frac{d y}{d x}\left(\frac{1}{2 \sqrt{y+x}}+\frac{1}{2 \sqrt{y-x}}\right)=\frac{1}{2 \sqrt{y-x}}-\frac{1}{2 \sqrt{y+x}}$$\frac{d y}{d x}\left(\frac{\sqrt{y-x}+\sqrt{y+x}}{2 \sqrt{y+x} \cdot \sqrt{y-x}}\right)=\frac{\sqrt{y+x}-\sqrt{y-x}}{(2 \sqrt{y-x} \cdot \sqrt{y+x})}$$\frac{d y}{d x} \times[\sqrt{y-x}+\sqrt{y+x}]=[\sqrt{y+x}-\sqrt{y-x}]$$\frac{d y}{d x}=\frac{\sqrt{y+x}-\sqrt{y-x}}{\sqrt{y+x}+\sqrt{y-x}}$Rationalizing the denominator
$\frac{d y}{d x}=\frac{(\sqrt{y+x}-\sqrt{y-x})(\sqrt{y+x}-\sqrt{y-x})}{(\sqrt{y+x}+\sqrt{y-x})(\sqrt{y+x}-\sqrt{y-x})}$$=\frac{(\sqrt{y+x}-\sqrt{y-x})^{2}}{(\sqrt{y+x})^{2}-(\sqrt{y-x})^{2}}$ $\left[\because a^{2}-b^{2}=(a+b)(a-b)\right]$$\frac{d y}{d x}=\frac{(\sqrt{y+x})^{2}+(\sqrt{y-x})^{2}-2 \sqrt{y+x} \cdot \sqrt{y-x}}{(y+x)-(y-x)}$$=\frac{y+x+y-x-2 \sqrt{y+x} \cdot \sqrt{y-x}}{y+x-y+x}$$=\frac{2 y-2 \sqrt{y+x} \cdot \sqrt{y-x}}{2 x}$$=\frac{2(y-\sqrt{y+x} \cdot \sqrt{y-x})}{2 x}$$=\frac{y-\sqrt{y+x} \cdot \sqrt{y-x}}{x}$$=\frac{y-\sqrt{y^{2}-x^{2}}}{x}$$=\frac{y}{x}-\frac{\sqrt{y^{2}-x^{2}}}{\sqrt{x^{2}}}$$\therefore \frac{d y}{d x}=\frac{y}{x}-\sqrt{\frac{y^{2}}{x^{2}}-1}$Thus proved
RD Sharma Class 12th Exercise 10.4 has a total of 31 questions including subparts, that are divided into two levels. Level 1 sums are less complex and can be solved using the fundamentals. In contrast, Level 2 sums are lengthy and require additional knowledge. Therefore, students should divide their work and study accordingly because they cannot cover the entire topic in one go.
The Level 1 questions in example 10.4 cover topics like finding dy/dx of quadratic and trigonometric equations, prove that sums, evaluation sums, etc. Level 2, On the other hand, contains questions mainly consisting of finding dy/dx at given parameters.
As Differentiation is a vast chapter, students should study efficiently to cover all topics within the stipulated time. Otherwise, it gets very strenuous to complete at the last moment. As RD Sharma's books are pretty extensive, solving all the problems is not an option. Instead, students should refer to this material to quickly gain an understanding of the concepts.
As RD Sharma Class 12th Exercise 10.4 material contains all the solutions in one place, it is very easy for revision. Teachers won't be able to cover hundreds of problems in their lectures. Students can compare their progress and stay on top of their Class with the help of RD Sharma Class 12 Chapter 10 Exercise 10.4 solutions.
After the introduction of such precise solved materials, The traditional textbook reference method is long gone. Instead, it has been found that students understand topics even better and can study efficiently with the help of solved materials. These materials are the key to scoring good marks, which is why students should start preparing from these sources without wasting any time.
As there are different ways towards solving a problem in Differentiation, students can find the easiest of them and solve accordingly with the help of this material. These expert-created solutions are updated to the latest version of the book, which means there would be no missing questions or additional questions. Moreover, the answers are provided by Brainly to help students in their exam preparation. This is why RD Sharma Class 12th Exercise 10.4 is free and accessible through their website. This means that you can access them anywhere, anytime, with an internet connection.