RD Sharma books are considered the gold standard for CBSE. They are informative, easy to understand, and exam-oriented, making them the best choice for students.
RD Sharma Class 12th Exercise 18.8 covers the chapter ‘Indefinite Integrals.’ The questions from this exercise are divided into two parts Level 1and Level 2, based on difficulty and weightage. This exercise contains 52 questions, of which 44 are Level 1, and 8 are Level 2.
RD Sharma Class 12th Exercise 18.8 covers concepts like indefinite integration of trigonometric and logarithmic values. The Level 1 questions are fundamental and easy to solve if students know the basic concepts. In contrast, Level 2 sums are lengthier and require an in-depth understanding of the theorems.
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- RD Sharma Class 12 Solutions Chapter18 Indefinite Integrals - Other Exercise
- Indefinite Integrals Excercise:18.8
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RD Sharma Class 12 Solutions Chapter18 Indefinite Integrals - Other Exercise
Indefinite Integrals Excercise:18.8
Indefinite Integrals exercise 18.8 question 1
Answer:$\frac{1}{\sqrt{2}}log\left | tan\frac{x}{2} \right |+C$Hint:$cos2x=1-2sin^{2}x$Given:$\int \! \frac{1}{\sqrt{1-cos2x}}dx$Explanation:$\int \! \frac{1}{\sqrt{2sin^{2}\: x}}dx=\frac{1}{\sqrt{2}}\int \frac{1}{sin\: x}dx$$=\frac{1}{\sqrt{2}}\int cos \: ecxdx$ $\left [ \int cos \: ecx = log\left | tan\frac{x}{2} \right | \right ]$$=\frac{1}{\sqrt{2}} log\left | tan\frac{x}{2} \right |+C$Indefinite Integrals exercise 18.8 question 2
Answer:$\sqrt{2}log\left | tan\left ( \frac{\pi }{4}+\frac{x}{4} \right ) \right |+C$Hint:$cos 2\: x=2cos^{2}\: x-1$Given:$\int \frac{1}{\sqrt{1+cos\: x}}dx$Explanation:$\int \frac{1}{\sqrt{2cos^{2\: \frac{x}{2}}}}dx$ $\left[\begin{array}{c} 1+\cos 2 x=2 \cos ^{2} x \\ 1+\cos x=2 \cos ^{2} \frac{x}{2} \end{array}\right]$$=\frac{1}{\sqrt{2}}\int \frac{1}{cos\frac{x}{2}}dx$$=\frac{1}{\sqrt{2}}\int \! sec\frac{x}{2}dx$$Let \frac{x}{2}=t$$dx=2dt$$=\frac{2}{\sqrt{2}} \int sec\: t\: dt =\sqrt{2} \int sec\: t\: dt$$=\sqrt{2}\: log\left | tan \left ( \frac{\pi }{4}+\frac{t}{2} \right ) \right |+C$ $\because \int\! sec\: x\: dx= log\: \left | tan \left ( \frac{\pi }{4}+\frac{x}{2} \right ) \right |$$=\sqrt{2}\: log\! \left | tan \left ( \frac{\pi }{4}+\frac{x}{2} \right ) \right |+C$
$log\left | sin\: x \right |+C$Hint:$cos\: 2x=2cos^{2}\: x-1=1-2sin^{2}x$Given:$\int \sqrt{\frac{1+cos\: 2x}{1-cos\: 2x}}dx$Explanation:$\int \sqrt{\frac{2cos^{2}\: x}{2sin^{2}\: x}}dx$ $\left[\begin{array}{c} 1+\cos 2 x=2 \cos ^{2} x \\ 1-\cos 2x=2 \sin ^{2} x \end{array}\right]$$=\int \sqrt{\left(\frac{\cos x}{\sin x}\right)^{2}} d x$$=\int cot\; xdx$$=log\left | sin\; x \right |+C$Indefinite Integrals exercise 18.8 question 4
Answer:$-2log\left | cos\frac{x}{2} \right |+C$Hint:$cos \: 2\: x=2cos^{2}\: x-1=1-2sin^{2}\: x$Given:$\int \sqrt{\frac{1-cos\: x}{1+cos\: x}}dx$Explanation:$\int \sqrt{\frac{2sin^{2}\frac{x}{2}}{2cos^{2}\frac{x}{2}}}dx$ $[cos\: x=2cos^{2}\: \frac{x}{2}-1\: \: or\; \; 1-2sin^{2}\frac{x}{2}]$$\int tan\frac{x}{2}dx$$Let \frac{x}{2}=t$$dx=2dt$$2\int tan\: tdt=-2log\left | cos\: t \right |+C$$=-2log\left | cos\: \frac{x}{2} \right |+C$Indefinite Integrals exercise 18.8 question 5
Answer:$2sin\: x-log\left | sec\: x+tan\; x \right |+C$Hint:$sec\: x=\frac{1}{cos\: x}$Given:$\int \frac{sec\: x}{sec\: 2x }dx$Explanation:$\int\left(\frac{1}{\cos x}\right)\left(\frac{1}{\frac{1}{\cos 2 x}}\right) d x$$=\int\! \frac{cos\: 2x}{cos\: x}dx$$=\int\! \frac{2cos^{2}\: x-1}{cos\: x}dx$$=\int\!2\frac{cos^{2}x}{cos\: x}dx-\frac{1}{cos\: x}dx$$=2\! \int\!cos\: xdx-\int\! sec\: xdx$$=2 sin\; x-log\left | sec\: x +tan\: x\right |+C$Indefinite Integrals exercise 18.8 question 6
Answer:$log\: log\left | sin\: sin\: x+cos\: cos\: x \right |+C$Hint:$cos^{2}\: x-sin^{2}\: x=cos2x$Given:$\int\! \frac{cos2x}{(cos\: x+sin\: x)^{2}}dx$Explanation:$\int\! \frac{cos^{2}-sin^{2}x}{(cos\: x+sin\: x)^{2}}dx$$=\int\! \frac{(cos\: x+sin\: x)(cos\: x-sin\: x)}{(cos\: x+sin\: x)^{2}}dx$$=\int\! \frac{cos\: x-sin\: x}{cos\: x+sin\: x}dx$$Let \; \; cos\: x+sin\: x=t$$(-sin\: x+cos\: x)dx=dt$$=\int \! \frac{1}{t}dt$$=log\left | t \right |+C$$=log\left | cos\: x+sin\: x \right |+C$Indefinite Integrals exercise 18.8 question 7
Answer:$xcos(b-a)+sin(b-a)log\left | sin(x-b) \right |+C$Hint:$sin(A+B)=sinA\: cosB+cosA\: sinB$Given:$\int \! \frac{sin(x-a)}{sin(x-b)}dx$Explanation:$\int \! \frac{sin(x-a)}{sin(x-b)}dx$$=\int\frac{sin(x-a+b-b)}{sin(x-b)}dx$ $[add\; and\; subtract \: b\: in\; (x-a)]$$=\int \! \frac{sin(x-b+b-a)}{sin(x-b)}dx$$=\int \! \frac{sin(x-b)cos(b-a)+cos(x-b)sin(b-a)}{sin(x-b))}dx$ $[sin(A+B)=sinA\: cosB+cosA\: sinB]$$=\int \frac{\sin (x-b) \cos (b-a)}{\sin (x-b)} d x+\int \frac{\cos (x-b) \sin (b-a)}{\sin (x-b)} d x$$=\int\! cos(b-a)dx+\int \! cot(x-b)sin(b-a)dx$$=cos(b-a)\int dx+sin(b-a)\int cot(x-b)dx$$= cos(b-a)x+ sin(b-a)\: log\left | sin(x-b) \right |+C$$[\int\! cot\: x\: dx= log\left | sin\; x \right |+C]$
Answer:$x\: cos\: cos\: 2a-sin\: sin\: 2a \: log\: log\left | sin\: sin(x+a) \right |+C$Hint:$sin(A+B)=sinA\; cosB-cosA\; sinB$Given:$\int \! \frac{sin(x-a)}{sin(x+a)}dx$Explanation:$\int \! \frac{sin(x-a+a-a)}{sin(x+a)}dx$ $[Add\; and\; subtract\; a\; in\; (x-a) ]$$=\int \! \frac{sin(x+a-2a)}{sin(x+a)}dx$$=\int \! \frac{sin(x+a)cos2a-cos(x+a)sin2a}{sin(x+a)}dx$$=\int \! \frac{sin(x+a)cos2a}{sin(x+a)}dx-\int \! \frac{cos(x+a)sin2a}{sin(x+a)}dx$$=\int \!cos2a\, dx-\int \! cot(x+a)sin2a\, dx$$=cos2a\int \! dx-sin2a\int cot(x+a)dx$$=cos2ax-sin2a\; log\left | sin(x+a) \right |+C$$=xcos2a-sin2a\; log\left | sin(x+a) \right |+C$Indefinite Integrals exercise 18.8 question 9
Answer:$-log\left | cos\: x-sin\: x \right |+C$Hint:$tan\: x=\frac{sin\: x}{cos\: x}$Given:$\int \! \frac{1+tan\: x}{1-tan\: x}dx$Explanation:$\int \! \frac{1+\frac{sin\: x}{cos\: x}}{1-\frac{sin\: x}{cos\: x}}dx=\int \! \frac{cos\: x+sin\: x}{cos\: x-sin\: x}dx$Let,
$cos\: x-sin\: x=t$$(-sin\: x-cos\: x)dx=dt$$=\int \! \frac{dt}{t}$$=-log\left | t \right |$$=-log\left | cos\: x-sin\: x \right |+C$Indefinite Integrals exercise 18.8 question 10
Answer:$(x-a)cos\: a-sin\: a\: log\left | sec(x-a) \right |+C$Hint:$cos(A+B)=cosA\: cosB-sinA\: sinB$Given:$\int \! \frac{cosx}{cos(x-a)}dx$Explanation:$\int \! \frac{cos(x-a+a)}{cos(x-a)}dx$[Add and subtract
$a$ in
$x$]
$=\int \! \frac{cos(x-a)cos\: a-sin(x-a)sin\: a}{cos(x-a)}dx$$=\int \! \frac{cos(x-a)cos\: a}{cos(x-a)}dx-\int \! \frac{sin(x-a)sin\: a}{cos(x-a)}dx$$=\int \! cos\: a\: dx-\int \! tan(x-a)sin\: a\: dx$$\therefore xcos\: a-sin\: a\: log\left | sec(x-a) \right |+C$
Answer:$log\left | cos(\frac{\pi }{4}-x) \right |+C$Hint:$sin^{2}x+cos^{2}x=1\; and\; sin\: 2x=2sin\: x\, cos\: x$Given:$\int \! \sqrt{\frac{1-sin2x}{1+sin2x}}dx$Explanation:$\int \! \sqrt{\frac{sin^{2}x+cos^{2}x-2sin\: x\: cos\: x}{sin^{2}x+cos^{2}x+2sin\: x\: cos\: x}}dx$$=\int \! \sqrt{\frac{(sin\: x-cos\: x)^{2}}{(sin\: x+cos\: x)^{2}}}dx$$=\int \! \sqrt{(\frac{sin\: x-cos\: x}{sin\: x+cos\: x}})^{2}dx$$=\int \! {\frac{sin\: x-cos\: x}{sin\: x+cos\: x}}dx$$=\int \!\frac{\frac{sin\: x}{cos\: x}-\frac{cos\: x}{cos\: x}}{\frac{sin\: x}{cos\: x}+\frac{cos\: x}{cos\: x}}dx$$=\int \!\frac{tan\: x-1}{tan\: x+1}dx$$=\int \!\frac{tan\: x-tan\frac{\pi }{4}}{1+tan\: x\: tan\frac{\pi }{4}}dx$ $[tan\frac{\pi }{4}=1]$$=\int \! tan(x-\frac{\pi }{4})dx$$=-\int \! tan(\frac{\pi }{4}-x)dx$$=-[-log\left | cos(\frac{\pi }{4}-x) \right |+C]$$=log\left | cos(\frac{\pi }{4}-x) \right |+C$Indefinite Integrals exercise 18.8 question 12
Answer:$\frac{1}{3}log\left | e^{3x}+1 \right |+C$Hint:$\int \! e^{x}dx=e^{x}+C\; \; \; \; or\; \; \; \; \int \! \frac{1}{x}dx=log\left | x \right |+C$Given:$\int \! \frac{e^{3x}}{e^{3x}+1}dx$Explanation:${e^{3x}+1}=t$$3e^{3x}dx=dt$$=\frac{1}{3}\! \int \! \frac{dt}{t}$$=\frac{1}{3}log\left | t \right |$$=\frac{1}{3}log\left | e^{3x} \right |+C$Indefinite Integrals exercise 18.8 question 13
Answer:$\frac{1}{3}log\left | 3sec\; x+5 \right |C$Himt:$\int \! \frac{1}{x}dx=log\left | x \right |+C$Given:$\int \! \frac{sec\: x\: tan\: x}{3sec\: x+5}dx$Explanation:Let,
$3sec\: x+5=t$$3sec\: x \: tan \: xdx=dt$$=\int \! \frac{dt}{3t}=\frac{1}{3}\int \! \frac{dt}{t}$$=\frac{1}{3}log \: t+C$$=\frac{1}{3}log \: \left | 3sec\: x+5 \right |+C$Indefinite Integrals exercise 18.8 question 14
Answer:$-log\left | sin\; x+cos\: x \right |+C$Hint:$Cot\: x=\frac{cos\: x}{sin\: x}$Given:$\int \! \frac{1-cot\: x}{1+cot\: x}dx$Explanation:$\int \! \frac{1-\frac{cos\: x}{sin\: x}}{1+\frac{cos\: x}{sin\: x}}dx$ $=\int \! \frac{sin\: x-cos\: x}{sin\: x+cos\: x}dx$Let
$sin\: x+cos\: x=t$$(cos\: x-sin\: x)dx=dt$$=-\int \! \frac{dt}{t}\; \; \; \; =-log\: t+C$$=-log\left | sin\: x+cos\: x \right |+C$Indefinite Integrals exercise 18.8 question 15
Answer:$log\left | log(tan\: x) \right |+C$Hint:$tan\: x=\frac{sin\: x}{cos\: x},\: \: sec\: x=\frac{1}{cos\: x},\: \: cos\: ecx=\frac{1}{sin\: x}$Given:$\int \! \frac{sec\: x\: cos\: ecx}{log\left ( tan\: x \right )}dx$Explanation:Let
$log(tan\: x)=t$$\frac{1}{tan\: x}(sec^{2}x)dx=dt$$\Rightarrow \frac{sec\: x}{\frac{sin\: x}{cos\: x}}\times \frac{1}{cos\: x}dx=dt$$\Rightarrow sec\: x\: cos\: ecx\: dx=dt$$=\int \! \frac{dt}{t}\: \: \: =log\: t+C$$=log\left | log(tan\: x) \right |+C$Indefinite Integrals exercise 18.8 question 16
Answer:$log\left | 3+log\: x \right |+C$Hint:$\frac{\mathrm{d} }{\mathrm{d} x}(log\: x)=\frac{1}{x}$Given:$\int \! \frac{1}{x(3+log\: x)}dx$Explanation:Let
$(3+log\: x)=t$$\frac{1}{x}dx=dt$$=\int \! \frac{dt}{t}\: \: \: =log\: t+C$$=log\left | 3+log\: x \right |+C$Indefinite Integrals exercise 18.8 question 17
Answer:$log\left | e^{x}+x \right |+C$Hint:$\frac{\mathrm{d} }{\mathrm{d} x}(e^{x}+x)=e^{x}+1$Given:$\int \! \frac{e^{x}+1}{e^{x}+x}dx$Explanation:Let
$e^{x}+x=t$$(e^{x}+1)dx=dt$$=\int \! \frac{dt}{t}\: \: =log\: t+C$$=log\left | e^{x} +x\right |+C$Indefinite Integrals exercise 18.8 question 18
Answer:$log\left | log\: x \right |+C$Hint:$\frac{\mathrm{d} }{\mathrm{d} x}(log\: x)=\frac{1}{x}$Given:$\int \! \frac{1}{x\: log\: x}dx$Explanation:Let
$log\: x=t$$\frac{1}{x}dx=dt$$=\int \! \frac{dt}{t}$$=log\: t+C$$=log\left | log\: x \right |+C$Indefinite Integrals exercise 18.8 question 19
Answer:$\frac{1}{b-a}In\left | a\: cos^{2}\: x+b\: sin^{2}\: x \right |+C$Hint:$\int \! \frac{dt}{t}=log\left | t \right |+C$Given:$\int \! \frac{sin\: 2x}{a\: cos^{2}\: x+b\: sin^{2}x}dx$........(1)Explanation:Let
$a\: cos^{2}\: x+b\: sin^{2}x=t$$(2a\, cos\, x(-sin\, x)+b(2\, sin\, x)(cos\, x))dx=dt$$(b-a)[2\, cos\, x\, sin\, x]dx=dt$$(b-a)sin\, 2x\, dx=dt$$sin\, 2x\, dx=\frac{dt}{b-a}$Put in (1)
$\frac{1}{b-a}\int \! \frac{dt}{t}$$=\frac{1}{b-a}In\left | t \right |+C$$=\frac{1}{b-a}In\left | a\: cos^{2}\: x+b\: sin^{2} \right |+C$Indefinite Integrals exercise 18.8 question 20
Answer:$\frac{1}{3}log\left | 2+3\, sin\, x \right |+C$Hint:$\frac{\mathrm{d} }{\mathrm{d} x}(a+b\, sin\, x)=cos\, x$Given:$\int \! \frac{cos\, x}{2+3\, sin\, x}dx$.....(1)Explanation:Let
$2+3\, sin\, x=t$$3\, cos\, x\, dx=dt$$cos\, x\, dx=\frac{dt}{3}$Put in (1)
$\int \! \frac{dt}{3t}=\frac{1}{3}\int \! \frac{dt}{t}$$=\frac{1}{3}log\left | t \right |+C$$=\frac{1}{3}log\left | 2+3\, sin\, x\right |+C$Indefinite Integrals exercise 18.8 question 21
Answer:$log\left | x+cos\, x \right |+C$Hint:$\frac{\mathrm{d} }{\mathrm{d} x}(x+cos\, x)=1-sin\, x$Given:$\int \! \frac{1-sin\, x}{x+cos\, x}dx$Explanation:Let
$x+cos\; x=t$$(1-sin\, x)dx=dt$$\int \! \frac{dt}{t}=log\left | t \right |+C$$=log\left | x+cos\, x \right |+C$Indefinite Integrals exercise 18.8 question 22
Answer:$-\frac{a}{b}log\left | be^{-x}+c \right |+C$Hint:$\int \! \frac{dt}{t}=log\left | t \right |+C$Given:$\int\! \! \frac{a}{b+ce^{x}}dx$Explanation:$\int\! \! \frac{a}{e^{x}(\frac{b}{e^{x}}+c)}dx$.......(1)$=\int\! \! \frac{ae^{-x}}{be^{-x}+c}dx$Let
$be^{-x}+c=t$$-e^{-x}(b)dx=dt$$e^{-x}dx=-\frac{1}{b}dt$Put in (1)
$\int \! \frac{a (-\frac{1}{b})dt}{t}$$=-\frac{a}{b}\int \! \frac{dt}{t}$$=-\frac{a}{b}log\left | t \right |+C$$=-\frac{a}{b}log\left | be^{-x}+c \right |+C$Indefinite Integrals exercise 18.8 question 23
Answer:$-log\left | e^{-x}+1 \right |+C$Hint:$\int \! \frac{1}{x}dx=log\left | x \right |+C$Given:$\int \! \frac{1}{e^{x}+1}dx$Explanation:$\int \! \frac{1}{e^{x}(1+\frac{1}{e^{x}})}dx\; \; \; \; =\int \! \frac{e^{-x}}{e^{-x}+1}dx$....(1)Let
$e^{-x}+1=t$$e^{-x}dx=-dt$From (1)
$\int \! \frac{-dt}{t}=-log\left | t \right |+C$$=-log\left | e^{-x}+1 \right |+C$Indefinite Integrals exercise 18.8 question 24
Answer:$log\left | log\: sin\: x \right |+C$Hint:$cot\: x=\frac{cos\: x}{sin\: x}$Given:$\int\! \frac{cot\: x}{log\: sin\: x}dx$ ........(1)Explanation:Let
$log\: sin\: x=t$$\frac{1}{sin\: x}(cos\: x)dx=dt$$cot\: x\: dx=dt$Put in (1)
$\int\! \frac{dt}{t}=log\left | t \right |+C$$=log\left | log\: sin\: x \right |+C$Indefinite Integrals exercise 18.8 question 25
Answer:$\frac{1}{2}log\left | e^{2x}-2 \right |+C$Hint:$\int \frac{1}{t}dt=log\left | t \right |+C$Given:$\int \frac{e^{2x}}{e^{2x}-2}dx$ .........(1)Explanation:Let
$e^{2x}-2=t$$2e^{2x}dx=dt$$e^{2x}dx=\frac{dt}{2}$Put (1) we get
$\int\! \frac{dt}{2t}=\frac{1}{2}\int \! \frac{dt}{t}$$=\frac{1}{2}log\left | t \right |+C$$=\frac{1}{2}log\left | e^{2x}-2 \right |+C$Indefinite Integrals exercise 18.8 question 26
Amswer:$\frac{1}{2}log\left | 6cos\, x+4sin\, x \right |+C$Hint:$\int \! \frac{1}{t}dt=log\left | t \right |+C$Given:$\int \! \frac{2cos\, x-3sin\, x}{6cos\, x+4sin\, x}dx$......(1)Explanation:Let
$6cos\, x+4sin\, x=t$$(-6sin\, x+4cos\, x)dx=dt$$2(2cos\, x-3sin\, x)dx=dt$Put in (1)
$\int \! \frac{dt}{2t}$$\frac{1}{2}\int \! \frac{dt}{t}=\frac{1}{2}log\left | t \right |+C$$=\frac{1}{2}log\left | 6cos\, x+4sin\, x \right |+C$Indefinite Integrals exercise 18.8 question 27
Answer:$\frac{1}{2}log\left | x^{2}+sin\, 2x+2x \right |+C$Hint:$\int\! \frac{1}{t}dt=log\left | t \right |+C$Given:$\int\! \frac{cos\, 2x+x+1}{x^{2}+sin\, 2x+2x}dx$.......(1)Explanation:Let
$x^{2}+sin\, 2x+2x=t$$(2x+2cos\, 2x+2)dx=dt$$2(x+cos\, 2x+1)dx=dt$From (1)
$\frac{1}{2}\int \! \frac{dt}{t}=\frac{1}{2}log\left | t \right |+C$$=\frac{1}{2}log\left | x^{2}+sin\, 2x+2x \right |+C$Indefinite Integrals exercise 18.8 question 28
Answer:$\frac{1}{sin(b-a)}[log(\frac{sec(x+b)}{sec(x+a)})]+C$Hint:$M\! ultipl\! y\; and\; divide\; by\; sin(b-a)$Given:$\int \! \frac{1}{cos(x+a)cos(x+b)}dx$......(1)Explanation:$M\! ultipl\! y\; and\; divide\; by\; sin(b-a)$From (1)
$=\frac{1}{sin(b-a)}\int \! \frac{sin(b-a)}{cos(x+a)cos(x+b)}dx$$=\frac{1}{sin(b-a)}\int \! \frac{sin[(x+b)-(x+a)]}{cos(x+a)cos(x+b)}dx$ Add and subtract
$x$ in
$b-a$$=\frac{1}{sin(b-a)}\int \! \frac{sin(x+b)cos(x+a)-sin(x+a)cos(x+b)}{cos(x+a)cos(x+b)}dx$$=\frac{1}{sin(b-a)}[\int \! \frac{sin(x+b)}{cos(x+b)}dx-\int \! \frac{sin(x+a)}{cos(x+a)}dx]$$=\frac{1}{sin(b-a)}[\int \! tan(x+b)dx-\int \! tan(x-a)dx]$$=\frac{1}{sin(b-a)}[log\left | sec(x+b) \right |-log\left | sec(x+a) \right |]+C$$=\frac{1}{sin(b-a)}[log\left | \frac{sec(x+b)}{sec(x+a)} \right |]+C$ $[log\, a-log\, b=log\frac{a}{b}]$Indefinite Integrals exercise 18.8 question 29
Answer:$log\left | 2sin\, x+cos\, x \right |+C$Hint:$\int \! \frac{dt}{t}=log\left | t \right |+C$Given:$\int \! \frac{-sin\, x+2cos\, x}{2sin\, x+cos\, x}dx$....(1)Explanation:Let
$2sin\, x+cos\, x=t$$(2cos\, x-sin\, x)dx=dt$From (1)
$\int \! \frac{dt}{t}=log\left | t \right |+C$$=log\left | 2sin\, x+cos\, x \right |+C$Indefinite Integrals exercise 18.8 question 30
Answer:$\frac{1}{3}log\left | cos\, 3x \right |+C$Hint:$U\! se\; cos\, A-cos\, B \: and\: sin\, A-sin\, B f\! ormula$Given:$\int \! \frac{cos4x-cos2x}{sin4x-sin2x}dx$Explanation:$\int \frac{-2 \sin \left(\frac{4 x-2 x}{2}\right) \sin \left(\frac{4 x+2 x}{2}\right)}{2 \cos \left(\frac{4 x+2 x}{2}\right) \sin \left(\frac{4 x-2 x}{2}\right)} d x \quad\left[\begin{array}{l} \cos A-\cos B=-2 \sin \left(\frac{A+B}{2}\right) \sin \left(\frac{A-B}{2}\right) \\ \sin A-\sin B=2 \cos \left(\frac{A+B}{2}\right) \sin \left(\frac{A-B}{2}\right) \end{array}\right]$$=-\int \! \frac{sin3x}{cos3x}dx$$=-\int \! \tan\, 3xdx$$=-[\frac{-log\left | cos\, 3x \right |}{3}]+C$$=\frac{1}{3}log\left | cos\, 3x \right |+C$Indefinite Integrals exercise 18.8 question 31
Answer:$log\left | log(sec\, x+tan\, x) \right |+C$Hint:$\int \! \frac{dt}{t}=log\left | t \right |+C$Given:$\int \! \frac{sec\, x}{log(sec\, x+tan\, x)}dx$......(1)Explanation:Let
$log(sec\, x+tan\, x)=t$$\frac{1}{sec\, x+tan\, x}(sec\, x\: tan\, x+sec^{2}x)dx=dt$$\Rightarrow \frac{\frac{sin\, x}{cos^{2}x}+\frac{1}{cos^{2}x}}{\frac{sin\, x}{cos\, x}+\frac{1}{cos\, x}}dx=dt$$\Rightarrow \frac{\frac{1+sin\, x}{cos^{2}x}}{\frac{1+sin\, x}{cos\, x}}dx=dt$$=sec\, xdx=dt$Put in (1)
$\int \! \frac{dt}{t}=log\left | t \right |+C$$=log\left | log(sec\, x+tan\, x) \right |+C$Indefinite Integrals exercise 18.8 question 32
Answer:$log\left | log \: tan\frac{x}{2} \right |+C$Hint:$sin\, 2x=2sin\, x\, cos\, x$Given:$\int \! \frac{cos\, ecx}{log\, tan\frac{x}{2}}dx$.....(1)Explanation:Let
$log\, tan\frac{x}{2}=t$$\frac{1}{tan\frac{x}{2}}sec^{2}\frac{x}{2}(\frac{1}{2})dx=dt$$\frac{1}{2cos\frac{x}{2}sin\frac{x}{2}}dx=dt$$\frac{1}{sin2\times \frac{x}{2}}dx=dt$$cos\, ecx\, dx=dt$Put in (1)
$\int \! \frac{dt}{t}=log\left | t \right |+C$$=log\left | log \: tan\frac{x}{2} \right |+C$Indefinite Integrals exercise 18.8 question 33
Answer:$=log\left | log(log\, x) \right |+C$Hint:$log(log\, x)=t$$\frac{1}{log\, x(x)}dx=dt$Given:$\int \! \frac{1}{x\, log\, x\, log(log\, x)}dx$....(1)Explanation:Let
$log\, (log\, x)=t$$\frac{1}{log\, x\times x}dx=dt$$\frac{dx}{x\, log\, x}=dt$From (1) we get
$\int \! \frac{dt}{t}=log\left | t \right |+C$$=log\left | log(log\, x) \right |+C$Indefinite Integrals exercise 18.8 question 34
Answer:$-log\left | 1+cot\, x \right |+C$Hint:$\frac{\mathrm{d} }{\mathrm{d} x}cot\, x=-cos\, ec^{2}x$Given:$\int \! \frac{cos\, ec^{2}x}{1+cot\, x}dx$.....(1)Explanation:Let
$1+cot\, x=t$$-cos\, ec^{2}xdx=dt$From (1)
$-\int \! \frac{dt}{t}=-log\left | t \right |+C$$=-log\left | 1+cot\, x \right |+C$Indefinite Integrals exercise 18.8 question 35
Answer:$log\left | 10^{x}+x^{10} \right |+C$Hint:$\frac{\mathrm{d} }{\mathrm{d} x}(10^{x}+x^{10})=10x^{9}+10^{x}log_{e}10$Given:$\int \! \frac{10x^{9}+10^{x}log_{e}10}{10^{x}+x^{10}}dx$.......(1)Explanation:Let
$10^{x}+x^{10}=t$$(10x^{9}+10^{x}log_{e}10)dx=dt$From (1) we get
$\int \! \frac{dt}{t}=log\left | t \right |+C$$=log\left | 10^{x}+x^{10} \right |+C$Indefinite Integrals exercise 18.8 question 36
Answer:$log\left | x+cos^{2}x \right |+C$Hint:Put denominator=t
Given:$\int \! \frac{1-sin\, 2x}{x+cos^{2}x}dx$.......(1)Explanation:Let
$x+cos^{2}x=t$$[1+2cos\, x(-sin\, x)]dx=dt$$(1-2sin\, x\, cos\, x)dx=dt$$(1-2sin\, 2x)dx=dt$Put in (1) we get
$\int \! \frac{dt}{t}=log\left | t \right |+C$$=log\left | x+cos^{2}x \right |+C$Indefinite Integrals exercise 18.8 question 37
Answer:$log\left | x+log\, sec\, x \right |+C$Hint:Put denominator = t
Given:$\int \! \frac{1+tan\, x}{x+log\, sec\, x}dx$......(1)Explanation:Let
$x+log\, sec\, x=t$$[1+\frac{1}{sec\, x}(sec\, x\, tan\, x)]dx=dt$$(1+tan\, x)dx=dt$Put in (1)
$\int \frac{dt}{t}=log\left | t \right |+C$$=log\left | x+log\, sec\, x \right |+C$Indefinite Integrals exercise 18.8 question 38
Answer:$\frac{1}{b^{2}}log(a^{2}+b^{2}sin^{2}x)+C$Hint:Put denominator = t
Given:$\int \! \frac{sin\, 2x}{a^{2}+b^{2}sin^{2}x}dx$......(1)Explanation:Let
$a^{2}+b^{2}sin^{2}x=t$$b^{2}(2sin\, xcos\, x)dx=dt$$b^{2}sin\, 2xdx=dt$$sin\, 2xdx=\frac{dt}{b^{2}}$Put in (1) we get
$\int \! \frac{dt}{b^{2}(t)}$$=\frac{1}{b^{2}}\int \! \frac{dt}{t}$$=\frac{1}{b^{2}}log\left | t \right |+C$$=\frac{1}{b^{2}}log(a^{2}+b^{2}sin^{2}x)+C$Indefinite Integrals exercise 18.8 question 39
Answer:$log\left | x+log\, x \right |+C$Hint:Put
$x+log\, x=t$$(x+\frac{1}{x})dx=dt$$\frac{x+1}{x}dx=dt$Given:$\int \! \frac {x+1}{x(x+log\, x)}dx$....(1)Explanation:Let
$x+log\, x=t$$(x+\frac{1}{x})dx=dt$$(\frac{x+1}{x})dx=dt$Put in (1) we get
$\int \! \frac{dt}{t}$$=log\left | t \right |+C$$=log\left | x+log\, x \right |+C$Indefinite Integrals exercise 18.8 question 40
Answer:$\frac{1}{3}log\left | 2+3sin^{-1}x \right |+C$Hint:$\frac{\mathrm{d} }{\mathrm{d} x} sin^{-1}x=\frac{1}{\sqrt{1-x^{2}}}$Given:$\int \! \frac{1}{\sqrt{1-x^{2}}(2+3sin^{-1}x)}dx$......(1)Explanation:Let
$2+3sin^{-1}x=t$$\frac{3}{\sqrt{1-x^{2}}}dx=dt$$\frac{dx}{\sqrt{1-x^{2}}}=\frac{dt}{3}$Put in (1) we get
$\frac{1}{3}\int \! \frac{dt}{t}=\frac{1}{3}log\left | t \right |+C$$=\frac{1}{3}log\left | 2+3sin^{-1}x \right |+C$Indefinite Integrals exercise 18.8 question 41
Answer:$log\left | tan\, x+2 \right |+C$Hint:$\frac{\mathrm{d} }{\mathrm{d} x}(tan\, x)=sec^{2}x$Given:$\int \! \frac{sec^{2}x}{tan\, x+2}dx$....(1)Explanation:Let
$tan\, x+2=t$$sec^{2}xdx=dt$Put in (1)
$\int \! \frac{dt}{t}=log\left | t \right |+C$$=log\left | tan\, x+2 \right |+C$Indefinite Integrals exercise 18.8 question 42
Answer:$log\left | sin2x+tan\, x-5 \right |+C$Hint:Put denominator=t
Given:$\int \frac{2cos2x+sec^{2}x}{sin2x+tan\, x-5}dx$.....(1)Explanation:Let
$sin2x+tan\, x-5=t$$(2cos2x+sec^{2}x)dx=dt$Put in (1) we get
$\int \! \frac{dt}{t}=log\left | t \right |+C$$=log\left | sin2x+tan\, x-5 \right |+C$Indefinite Integrals exercise 18.8 question 43
Answer:$\frac{1}{3}log\left | sin3x \right |-\frac{1}{5}log\left | sin5x \right |+C$Hint:$sin(A-B)=sinAcosB-cosAsinB$Given:$\int \! \frac{sin2x}{sin5x\, sin3x}dx$Explanation:$\int \! \frac{sin(5x-3x)}{sin5x\, sin3x}dx$$=\int \! \frac{sin5x\, cos3x-cos5x\, sin3x}{sin5x\, sin3x}dx$$=\int \! \frac{cos3x}{sin3x}dx-\int \! \frac{cos5x}{sin5x}dx$$=\int \! \cot3xdx-\int \! cot5xdx$$=\frac{1}{3}log\left | sin3x \right |-\frac{1}{5}log\left | sin5x \right |+C$Indefinite Integrals exercise 18.8 question 44
Answer:$log\left | x+log\, sin\, x \right |+C$Hint:Put denominator = t
Given:$\int \! \frac{1+cot\, x}{x+log\, sin\, x}dx$........(1)Explanation:Let
$x+log\, sin\, x=t$$(1+\frac{1}{sin\, x}(cos\, x))dx=dt$$(1+cot\, x)dx=dt$Put in (1) we get
$\int \! \frac{dt}{t}=log\left | t \right |+C$$=log\left | x+log\, sin\, x \right |+C$Indefinite Integrals exercise 18.8 question 45
Answer:$cos(a-b)log\left | sin(x+b) \right |-xsin(a-b)+C$Hint:$cos(A+B)=cosAcosB-sinAsinB$Given:$\int \! \frac{cos(x+a)}{sin(x+b)}dx$Explanation:$=\int \! \frac{cos(x+a-b+b)}{sin(x+b)}dx$ ...adding and subtracting b in numerator
$=\int \! \frac{cos(x+b+a-b)}{sin(x+b)}dx$$=\int \! \frac{cos(x+b)cos(a-b)-sin(x+b)sin(a-b)}{sin(x+b)}dx$$=\int \! cot(x+b)cos(a-b)dx-\int \! sin(a-b)dx$$=cos(a-b)\int \! cot(x+b)dx-sin(a-b)\int \!dx$$=cos(a-b)log\left | sin(x+b) \right |-xsin(a-b)+C$Indefinite Integrals exercise 18.8 question 46
Answer:$2log\left | \sqrt{x}+1 \right |+C$Hint:Let
$\sqrt{x}=t$Given:$\int \! \frac{1}{\sqrt{x}(\sqrt{x}+1)}dx$.......(1)Explanation:Let
$\sqrt{x}=t$$\frac{1}{2\sqrt{x}}dx=dt$$\frac{dx}{\sqrt{x}}=2dt$From (1) we have
$\int \! \frac{2dt}{t+1}=2\int \! \frac{1}{t+1}dt$$=2log\left | t+1 \right |$$=2log\left | \sqrt{x}+1 \right |+C$Indefinite Integrals exercise 18.8 question 47
Answer:$-\frac{1}{5}log\left | cos5x \right |+\frac{1}{2}log\left | cos2x \right |+\frac{1}{3}log\left | cos3x \right |+C$Hint:$tan(A+B)=\frac{tanA+tanB}{1-tanA\, tanB}$Given:$\int \! tan2x\, tan3x\, tan5xdx$.....(1)Explanation:$tan5x=tan(2x+3x)=\frac{tan2x+tan3x}{1-tan2x\, tan3x}$Cross-multiplying$tan5x-tan5x\, tan2x\, tan3x=tan2x+tan3x$$tan5x-tan2x-tan3x=tan5x\, tan2x\, tan3x$Put in (1) we get
$\int \! (tan5x-tan2x-tan3x)dx$$=-\frac{1}{5}log\left | cos5x \right |+\frac{1}{2}log\left | cos2x \right |+\frac{1}{3}log\left | cos3x \right |+C$Indefinite Integrals exercise 18.8 question 48
Answer:$cot\, \theta log\left |\frac{cos\, x}{cos(x+\theta )} \right |+C$Hint:$tan2x=\frac{2tan\, x}{1-tan^{2}x}$Given:$\int \! [1+tan\, x\, tan\left | x+\theta \right |]dx$...(1)Explanation:$tan\, \theta =tan[x+\theta -x]=\frac{tan(x+\theta )-tan\, x}{1+tan\, x\, tan(x+\theta )}$$1+tan\, x\, tan(x+\theta )=cot\, \theta [tan(x+\theta )-tan\, x]$Put in (1)
$\int \! cot\, \theta [tan(x+\theta )-tan\, x]dx$$=cot\, \theta \int \! tan(x+\theta )dx-cot\, \theta \int \! tan\, xdx$$=cot\, \theta [-log\left | cos(x+\theta ) \right |+log\left | cos\, x \right |]+C$$=cot\, \theta log\left |\frac{cos\, x}{cos(x+\theta )} \right |+C$Indefinite Integrals exercise 18.8 question 49
Answer:$log\left | sin(x+\frac{\pi }{6})sin(x-\frac{\pi }{6}) \right |+C$Hint:$sin(A+B)=sinAcosB+cosAsinB$Given:$\int \! \frac{sin2x}{sin(x-\frac{\pi }{6})sin(x+\frac{\pi }{6})}dx$Explanation:$\int \! \frac{sin[(x-\frac{\pi }{6}+\frac{\pi }{6}+x)]}{sin(x-\frac{\pi }{6})sin(x+\frac{\pi }{6})}dx$$\int \! \frac{sin[(x-\frac{\pi }{6})+(x+\frac{\pi }{6})]}{sin(x-\frac{\pi }{6})sin(x+\frac{\pi }{6})}dx$$=\int \frac{\sin \left(x-\frac{\pi}{6}\right) \cos \left(x+\frac{\pi}{6}\right)+\cos \left(x-\frac{\pi}{6}\right) \sin \left(x+\frac{\pi}{6}\right)}{\sin \left(x-\frac{\pi}{6}\right) \sin \left(x+\frac{\pi}{6}\right)}$$=\int\! cot(x+\frac{\pi }{6})dx+\int \! cot(x-\frac{\pi }{6})dx$$=log\left | sin(x+\frac{\pi }{6}) \right |+log\left | sin(x-\frac{\pi }{6}) \right |+C$$=log\left | sin(x+\frac{\pi }{6})sin(x-\frac{\pi }{6}) \right |+C$Indefinite Integrals exercise 18.8 question 50
Answer:$\frac{1}{e}log\left | e^{x}+x^{e} \right |+C$Hint:$U\! se\: f\! ormula\: o\! f\int \! \frac{1}{t}=log(t)+c$Given:$\int \! \frac{e^{x-1}+x^{e-1}}{e^{x}+x^{e}}dx$....(1)Explanation:Let
$e^{x}+x^{e}=t$$(e^{x}+ex^{e-1})dx=dt$$e(e^{x-1}+x^{e-1})dx=dt$Put in (1)
$\frac{1}{e}\int \! \frac{dt}{t}=\frac{1}{e}log\left | t \right |+C$$=\frac{1}{e}log\left | e^{x}+x^{e} \right |+C$Indefinite Integrals exercise 18.8 question 51
Answer:$sec\, x+log\left | tan\frac{x}{2} \right |+C$Hint:$sin^{2}x+cos^{2}x=1$Given:$\int \! \frac{1}{sin\, x\, cos^{2}x}dx$Explanation:$\int \! \frac{sin^{2}x+cos^{2}x}{sin\, x\, cos^{2}x}dx$$=\int \! \frac{sin^{2}x}{sin\, x\, cos^{2}x}dx+\int \! \frac{1}{sinx}dx$$=\int \! tan\, xsec\, xdx+\int \! cos\, e\, cxdx$$=sec\, x+log\left | tan\frac{x}{2} \right |+C$Indefinite Integrals exercise 18.8 question 52
Answer:$\frac{1}{4}[cos\, ecx-log\left | sec\, x+tan\, x \right |]+C$Hint:$Put \; \; 1=sin^{2}x+cos^{2}x$Given:$\int \! \frac{1}{cos3x-cos\, x}dx$Explanation:$\int \! \frac{sin^{2}x+cos^{2}x}{cos3x-cos\, x}dx$$=\int \! \frac{sin^{2}x+cos^{2}x}{4cos^{3}x-3cos\, x-cos\, x}dx$ $cos3x=4cos^{3}x-3cos\, x$$=\int \! \frac{sin^{2}x+cos^{2}x}{4cos^{3}x-4cos\, x}dx$$=\int \! \frac{sin^{2}x+cos^{2}x}{4cos\, x(cos^{2}x-1)}dx$$=-\int \! \frac{sin^{2}x+cos^{2}x}{4cos\, x(sin^{2}x)}dx$ $sin^{2}x+cos^{2}x=1$$=-\int \! \frac{sin^{2}x}{4cos\, x\, sin^{2}x}dx+(-\int \! \frac{cos^{2}x}{4cos\, x\, sin^{2}x}dx)$$=-\frac{1}{4}\int \! \frac{1}{cos\, x}dx-\frac{1}{4}\int \! \frac{cos\, x}{ sin^{2}x}dx$$=-\frac{1}{4}\int \! sec\, xdx-\frac{1}{4}\int \! cot\, x\, cos\, e\, cxdx$$=-\frac{1}{4}log\left | sec\, x+tan\, x \right |-\frac{1}{4}(-cos\, e\, cx)+C$$=\frac{1}{4}[cos\, ecx-log\left | sec\, x+tan\, x \right |]+C$Indefinite Integrals exercise 18.9 question 62
Answer: $\frac{\sec ^{3} 2 x}{6}-\frac{\sec 2 x}{2}+c$Hint: Use substitution method to solve this integral
Given: $\int \tan ^{3} 2 \: x \cdot \sec 2 \: x \; d x$Solution:$\text { Let } I=\int \tan ^{3} 2 x \cdot \sec 2 x\; d x$$\Rightarrow I=\int \tan ^{2} 2 x \cdot \tan 2 x \cdot \sec 2 x\; d x$$\begin{aligned} &=\int\left(\sec ^{2} 2 x-1\right) \tan 2 x \cdot \sec 2 x \; d x \\ &=\int\left(\sec ^{2} 2 x \cdot \tan 2 x \cdot \sec 2 x-\tan 2 x \sec 2 x\right) d x \\ &=\int \sec ^{2} 2 x \cdot \tan 2 x \cdot \sec 2 x\; d x-\int \tan 2 x \cdot \sec 2 x\; d x \end{aligned}$$\begin{aligned} &\Rightarrow I=\int \sec ^{2} 2 x \cdot \tan 2 x \cdot \sec 2 x \; d x-\int \tan 2 x \cdot \sec 2 x\; d x \\ &\text { Put } \sec 2 x=t \Rightarrow \sec 2 x . \tan 2 x \cdot 2 \cdot d x=d t \end{aligned}$$\Rightarrow d x=\frac{d t}{2 \sec 2 x \cdot \tan 2 x} \text { then the Ist integral becomes }$$\Rightarrow I=\int t^{2} \cdot \tan 2 x \cdot \sec 2 x \cdot \frac{d t}{2 \sec 2 x \cdot \tan 2 x}-\int \sec 2 x \cdot \tan 2 x \; d x$$\begin{aligned} &=\int \frac{t^{2}}{2} d t-\int \sec 2 x \cdot \tan 2 x\; d x \\ &=\frac{1}{2} \int t^{2} d t-\int \sec 2 x \cdot \tan 2 x\; d x=\frac{1}{2} \frac{t^{2+1}}{2+1}-\frac{\sec 2 x}{2}+c \end{aligned}$$=\frac{1}{2} \cdot \frac{t^{3}}{3}-\frac{\sec 2 x}{2}+c \quad\left[\because \int x^{n} d x=\frac{x^{n+1}}{n+1}+c, \int \sec a x \cdot \tan a x \; d x=\frac{\sec a x}{a}+c\right]$$=\frac{1}{6} \sec ^{3} 2 x-\frac{\sec 2 x}{2}+c \quad[\because t=\sec 2 x]$
RD Sharma Class 12th Exercise 18.8 material is offered by carrier 360 to help students prepare well for their exams. However, as the chapter ‘Indefinite integrals’ contains hundreds of sums, it gets confusing for students to solve all of them. This is why Career360 has provided solutions for students to refer to and complete their syllabus efficiently. This way, they can ensure that no concept is left behind and every part of the syllabus is covered.
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