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    RD Sharma Class 12 Exercise FBQ The Plane Solutions Maths - Download PDF Free Online

    RD Sharma Class 12 Exercise FBQ The Plane Solutions Maths - Download PDF Free Online

    Lovekush kumar sainiUpdated on 25 Jan 2022, 11:52 AM IST

    RD Sharma books are the best books with regards to planning for board exams. However, board exams have consistently been viewed as a fabrication for some students. RD Sharma solutions In any case, when they allude to this book alongside Rd Sharma Class 12th Exercise FBQ solutions, they think that it is simpler to back out with a great deal of pressure and comprehend the idea in a vastly improved manner. This specific exercise has 20 inquiries from the general chapter. Rd Sharma Class 12th Exercise FBQ incorporates Equation of the plane containing two lines, Equation of the plane in scalar item structure, Reflection of point, Vector and Cartesian structure, condition of the plane in standard form, Shortest distance between two lines, and distance between the plane.

    This Story also Contains

    1. RD Sharma Class 12 Solutions Chapter28 FBQ The Plane - Other Exercise
    2. The Plane Exercise: FBQ
    3. RD Sharma Chapter-wise Solutions

    RD Sharma Class 12 Solutions Chapter28 FBQ The Plane - Other Exercise

    The Plane Exercise: FBQ

    The Plane exercise fill in the blank question 1

    Answer:
    10
    Hint:
    Use vector dot product
    Given:
    x + 2y - 2z = d, d>0
    Solution:
    Perpendicular distance of the plane ax +by + cz + d = 0
    $(x,y,z) \text { is } d = \left | \frac{ax_{1}+by_{1}+cz_{1}+d}{a^{2}+b^{2}+c^{2}} \right |$
    Equation of plane parallel to x + 2y - 2z = d is
    x + 2y -2z - d = 0 …………………………(1)
    Perpendicular distance from (1,-2,1) is S
    $\text { S } = \left | \frac{1-4-2+d}{\sqrt{1+4+4}} \right |\Rightarrow d=10$

    The Plane exercise fill in the blank question 2

    Answer:
    10
    Hint:
    Two perpendicular plane equals 0
    Given:
    3x - 6y - 2z = 7 and 2x + y - λz = 5
    Solution:
    The equations of planes are
    3x - 6y - 2z -7 =0
    and 2x + y - kz - 5 = 0
    Since two planes are perpendicular to each other
    ∴(3)(2) + (-6)(1) + (-2) (-k) = 0 ? a1a2+b1b2+c1c2=0
    ∴6 - 6 + 2k = 0 2k = 0
    k = 0

    The Plane exercise fill in the blank question 3

    Answer:
    2X + 3Y - Y2 + 4 = 0
    Hint:
    Parallel plane equation also equals to 0
    Given:
    (1,2,3) and parallel plane 2x + 3y - 4 = 0
    Solution:
    Equation of parallel to2x + 3y - y2 = 0 is given by
    2x + 3y - y2 + λ = 0
    Also It passes through (1,2,3)
    ? 2(1) + 3(2) - 4(3) + λ = 0 ? λ = 4
    ∴ required plane is 2x + 3y - y2 + 4 = 0

    The Plane exercise fill in the blank question 4

    Answer:
    $\frac{X-1}{2}=\frac{Y-2}{3}=\frac{Z-3}{6}$
    Hint:
    Use bracket method
    Given:
    (1,2,3) and normal to the plane 2x - 3y + 6z = 11
    Solution:
    Let the equation be
    $\frac{X-1}{2}=\frac{Y-2}{3}=\frac{Z-3}{6} = 0$
    $\sqrt{(1)^{2}+\left ( \frac{3}{2} \right )+\left ( \frac{6}{3} \right )}$
    ? we will get normal equation
    ? 2x - 3y + 6z = 11

    The Plane exercise fill in the blank question 5

    Answer:
    $k=\frac{1}{2}$
    Hint:
    Use vector 3 dimension
    Given:
    2x + 3y - 4k = 24 on the coordinate is 8
    Solution:

    $\therefore$ sum of intercepts
    =2 + 3 - 4k = 24

    The Plane exercise fill in the blank question 6

    Answer:
    3, -9
    Hint:
    Solve using fraction method.
    Given:
    (1,1,1) is half distance fromx + 2y + z + k = 0
    Solution:
    $\begin{aligned} &\sqrt{3}=\frac{1}{2}\left [ \frac{3+k}{\sqrt{3}} \right ]\\ &3=\pm \frac{1}{2}(3+k)\\ &3+k=\pm 6\\ &3+k=6 \qquad 3+k=6\\ &k=3 \qquad \qquad k=-9 \end{aligned}$

    The Plane exercise fill in the blank question 7

    Answer:
    (a,b,c)
    Hint:
    Let the points a,b,c and try to get the equation
    Given:
    $\frac{x}{a}+\frac{y}{b}+\frac{z}{c}=3$
    Solution:
    Let the point be (a,b,c)
    The plane meets the coordinates are at A,B and C such that centroid of the triangle ABC is (a,b,c)
    So, the plane cuts x- axis at (3a,0,0) , so, x- intercept = 3a
    The plane cuts z- axis at (0,0,3c)?z- intercept =3c
    The plane cuts y-axis at (0,3b,0)?y- intercept =3b
    ? all one getting the equation
    $\frac{x}{a}+\frac{y}{b}+\frac{z}{c}=3$
    ∴ the point will be (a,b,c)

    The Plane exercise fill in the blank question 8

    Answer:
    ax + by + cz = a2 + b2 + c2
    Hint:
    Firs find the co-ordinates
    Given:
    p(a,b,c) perpendicular to op
    Solution:
    The coordinates of the points o and p ,are (0,0,0) and (a,b,c) respectively. Therefore the direction rahos of op are (a-0)=a,(b-0) = b, and (c - 0) = c
    It is known that the equation of the plane passing through the point (x,y,z) is
    a(x - x1) + b(y - y1)+ c(z - z1) = 0
    ∴ the required equation will be
    a(x - a) + b(y - b) + c(z - c) = 0
    ax - a2 + by - b2 + cz - c2 = 0
    ax + by + cz = a2 + b2 + c2

    The Plane exercise fill in the blank question 9

    Answer:
    (2,2,2)
    Hint:
    Let its intercept be λ
    Given:
    Sum of the reciprocals of its intercepts on the coordinates axis is 1/2
    Solution:
    Let the equation of the variable plane be
    $\frac{x}{a}+\frac{y}{b}+\frac{z}{c}=\lambda \dots \dots \dots \dots(1)$
    The intercepts on the coordinate axes are a,b,c
    Let the sum of reciprocals of intercept in constant =λ
    Therefore,
    $\frac{1}{a}+\frac{1}{b}+\frac{1}{c}=\lambda \Rightarrow \frac{(\frac{1}{\lambda })}{a}+\frac{(\frac{1}{\lambda })}{b}+\frac{(\frac{1}{\lambda })}{c}=\lambda$
    $\left ( \frac{1 }{\lambda },\frac{1 }{\lambda },\frac{1 }{\lambda } \right )$
    lies on the plane (1)
    Hence, the variable plane (1) always passes through
    the fixed point
    $\left ( \frac{1 }{(\frac{1}{2})},\frac{1 }{(\frac{1}{2})},\frac{1 }{(\frac{1}{2})}\Rightarrow 2,2,2 \right )$

    The Plane exercise fill in the blank question 10

    Answer:
    1
    Hint:
    Use formulae of circumantce after finding c0-ordinates
    Given:
    x + αy +2 = 5
    Solution:
    Given equation of plane
    $x + \alpha y +2=5\Rightarrow \frac{x}{5}+\frac{\alpha y}{5}+\frac{z}{5}=1$
    Comparing above equation with equation of plane in intercept from
    $\frac{x}{x_{1}}+\frac{y}{y_{1}}+\frac{z}{z_{1}}=1$
    $x_1=5,y_1=5,z_1=5$
    So coordinates of points A,B,C?A(5,0,0),B(0,5,0),C(0,0,5)
    Let circumentre D(x,y,z)
    $\therefore AD=\sqrt{(x-5)^{2}+y^{2}+z^{2}}, BD=\sqrt{x^{2}+(y-5)^{2}+z^{2}}, CD=\sqrt{x^{2}+y^{2}+(z-5)^{2}}$
    AD=BD=CD ? taking AD=BD
    $\Rightarrow \sqrt{(x-5)^{2}+y^{2}+z^{2}}=\sqrt{x^{2}+(y-5)^{2}+z^{2}}$
    On squaring both sides
    (x - 5)2 + y2 + z2 = x2 + (y - 5)2 + z2 ? 1 = 1
    ∴ from equation (1) ,x,y can be x=1, y=1
    ∴ α=1 (also)(by solving)

    The Plane exercise fill in the blank question 11

    Answer:
    -4
    Hint:
    Use vector dot product
    Given:
    $\frac{2x-1}{2}=\frac{2-y}{2}=\frac{2+z}{k}$
    is parallel to the plane 2x - y + z = 3
    Solution:
    $\begin{aligned} &\frac{x-x_{1}}{a}=\frac{y-y_{1}}{b}=\frac{z-z_{1}}{c}\\ &\Rightarrow \frac{x-\frac{1}{2}}{1}=\frac{y-2}{-2}=\frac{z+1}{9}\\ &\vec{x}=2\hat{i}-\hat{j}+\hat{k}, \quad \vec{b}=\hat{i}-2\hat{j}+\hat{k}\\ &\vec{x}.\vec{b}=0\Rightarrow 2+2+k=0\Rightarrow k=-4 \end{aligned}$

    The Plane exercise fill in the blank question 12

    Answer:
    -6
    Hint:
    Use direction ratios
    Given:
    $\frac{x-2}{3}=\frac{y-1}{-5}=\frac{z+2}{2}$
    Solution:
    The line is
    $\frac{x-2}{3}=\frac{y-1}{-5}=\frac{z+2}{2}$
    The direction radius of the line are(3,-5,2)
    As the line lies in the plane x + 3y - αz + 7 = 0
    We have $3-15-2\alpha+7=0\Rightarrow -2\alpha-5=0$
    $\\ \\ \alpha=-\frac{5}{2}$

    The Plane exercise Fill in the blank question 13

    Answer:
    -9
    Hint:
    Use direction ratios
    Given:
    $\frac{x+1}{\lambda }=\frac{y-1}{1}=\frac{z+2}{-4}$
    Solution:
    Let the given line is
    $\frac{x+1}{\lambda }=\frac{y-1}{1}=\frac{z+2}{-4}$
    Direction ratios are λ,1,-4
    And the given plane 2x+ 2y - 8z = -5
    Its direction ratios are 2,2,-4
    And the given line and plane are perpendicular, then
    λ(1) + 1(1) + (-4)(-8) = 0
    2λ + 2 + 16=0
    λ = -9

    The Plane exercise Fill in the blank question 14

    Answer:
    6x + 4y + 3z = 12 is the required equation of plane
    Hint:
    Equation of the plane that cut the coordinate axes =1
    Given:
    (2,0,0) , (0,3,0) and (0,0,4)
    Solution:
    We know that, equation of the plane that cut the coordinate axes at
    (2,0,0) , (0,3,0) and (0,0,4) is
    $\frac{x}{a}+\frac{y}{b}+\frac{z}{c}=1$
    Hence, the equation of plane passes through the points (2,0,0) , (0,3,0) and (0,0,4)
    is
    $\frac{x}{2}+\frac{y}{3}+\frac{z}{4}=1$
    = 6x + 4y + 3z = 12

    The Plane exercise fill in the blank question 15

    Answer:
    x + y + z = 2 is the required Cartesian product
    Hint:
    Use vector product
    Given:
    $\vec{r}.\left ( \hat{i}+\hat{j}+\hat{k} \right )=2$
    Solution:
    We have,
    $\begin{aligned} &\vec{r}.\left ( \hat{i}+\hat{j}+\hat{k} \right )=2\\ &\Rightarrow (x\hat{i}+y\hat{j}+z\hat{k}).\left ( \hat{i}+\hat{j}+2 \right )=2\\ &\Rightarrow x+y+z=2 \end{aligned}$

    The Plane exercise Fill in the blank question 16

    Answer:
    $-2,\frac{4}{3},\frac{-4}{5}$
    are the intercepts made by the plane
    Hint:
    Convert the given equation into intercept form
    Given:
    2x - 3y + 5z + 4 = 0
    Solution:
    First let’s convert the given equation to intercept form i.e
    $\frac{x}{a}+\frac{y}{b}+\frac{z}{c}=1$
    Where a,b,c are x,y nad z intercepts respectively
    Given,
    2x - 3y + 5z + 4 = 0
    ⇒ -2x + 3y - 5z = 4
    Dividing by 4 both sides
    $\frac{x}{-2}+\frac{y}{\frac{4}{3}}+\frac{z}{\frac{4}{-5}}=1$
    On comparing we have intercepts as
    $-2,\frac{4}{3},\frac{-4}{5}$

    The Plane exercise Fill in the blank question 17

    Answer:
    $sin^{-1}\left [ \frac{9}{\sqrt{156}} \right ]$
    is the angle between the line and the plane
    Hint:
    Find $\theta$ using vector dot product
    Given:
    $\vec{r}=\left ( 5\hat{i}-\hat{j}-4\hat{k} \right )+\lambda \left ( 2\hat{i}-\hat{j}-\hat{k} \right ) \text { and the plane }\vec{r}. \left ( 3\hat{i}-4\hat{j}-\hat{k} \right )+5=0$
    Solution:
    Line
    $\vec{r}=\left ( 5\hat{i}-\hat{j}-4\hat{k} \right )+\lambda \left ( 2\hat{i}-\hat{j}-\hat{k} \right )$
    Is parallel to the vector
    $\vec{b}= 2\hat{i}-\hat{j}+\hat{k}$
    Normal to the plane is
    $\vec{n}= 3\hat{i}-4\hat{j}-\hat{k}$
    Let $\theta$ is the angle between line and plane
    Then,
    $sin\theta =\frac{\left | \vec{b}.\vec{n} \right |}{\left | \vec{b} \right |\left | \vec{n} \right |}\Rightarrow \frac{\left | \left ( 2\hat{i}-\hat{j}+\hat{k} \right ).\left ( 3\hat{i}-4\hat{j}+\hat{k} \right ) \right |}{\sqrt{6}.\sqrt{26}}$
    $=\frac{\left | 6+4-1 \right |}{\sqrt{156}}=\frac{9}{\sqrt{156}}$
    $\theta = sin^{-1}\left [ \frac{9}{\sqrt{156}} \right ]$

    The Plane exercise Fill in the blank question 18

    Answer:
    $\vec{r}.(5\hat{i}-3\hat{j}-2\hat{k})=38$
    is the required equation of plane.
    Hint:
    Use figure to solve the equation
    Given:
    (5,-3,-2)
    Solution:

    From the figure normal to the plane is
    $\vec{n}=\vec{OP}=(5\hat{i}-3\hat{j}-2\hat{k})$
    Plane passing through the point P(5,-3,-2)
    Equation of plane is
    $\begin{aligned} &5(x-5)-3(y+3)-2(z+2)=0\\ &5x-3y-2z=38 \end{aligned}$
    In vector form
    $\vec{r}.(5\hat{i}-3\hat{j}-2\hat{k})=38$

    The Plane exercise Fill in the blank question 19

    Answer:
    3 units is the required distance.
    Hint:
    use vector dot product to find the distance
    Given:
    $2x+y-2z-6=0 \text { and } 4x+2y-4z=0$
    Solution:
    Let
    $\begin{aligned} &P_{1}\rightarrow 2x+y-2z-6=0\\ &ax+by+cz+d_{1}=0\\ &P_{2}\rightarrow 4x+2y-4z=0\\ &ax+by+cz+d_{2}=0\\ \end{aligned}$
    $\begin{aligned} &\because P_{1}\left | \right |P_{2} \end{aligned}$
    $\begin{aligned} &\text { Distance between } P_{1} \text { and } P_{2}=\left | \frac{d_{2}-d_{1}}{\sqrt{a^{2}+b^{2}+c^{2}}} \right |\\ &=\left | \frac{0-6}{\sqrt{2^{2}+1^{2}+(-2)^{2}}} \right |=\left | \frac{-6}{4+1+4} \right |\\ &=3\: units \end{aligned}$

    The Plane exercise Fill in the blank question 20

    Answer:
    x - 3z = 10 is the required Cartesian equation
    Hint:
    use direction cosine formula.
    Given:
    P(1,0,-3)
    Solution:
    Assume direction cosine of the normal (a,b,c)
    Equation of plane passing through (x,y,z)
    $\begin{aligned} &\Rightarrow a(x-x_{1})+b(y-y_1)+c(z-z_1)=0\\ \end{aligned}$
    Point P(1,0,-3)
    $\begin{aligned} &\Rightarrow a(x-1)+b(y-0)+c(z-(-3))=0\\ \end{aligned}$
    Direction cosine of normal
    (a,b,c) = (1 - 0, 0 - 0, -3 - 0)
    (a,b,c) = (1,0,-3)
    Equation of the plane
    [(x - 1)+ 0 (y - 0) - 3 (2- (-3))]=0
    x - 3z = 10


    RD Sharma Class 12th Chapter 28 Exercise FBQ is arranged in a stepwise manner with hints for complex problems so that a student finds the perfect path to solve them when referring to these solutions. The benefits of these solutions are:

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