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Provide solution for RD Sharma maths class 12 chapter The Plane exercise 28.4 question 10

Answers (1)

Answer:

\vec{r}\left ( \frac{2}{\sqrt{29}}\hat{i}-\frac{3}{\sqrt{29}}\hat{j}+\frac{4}{\sqrt{29}}\hat{k} \right )=\frac{6}{\sqrt{29}} \text { and }2x-3y+4z=6 

Hint:

 You must know the rules of solving vector functions

Given:

 find the vector equation of the plane which is at a distance of

\frac{6}{\sqrt{29}}

from the origin and it’s normal vector from the origin is

2\hat{i}-3\hat{j}+4\hat{k}

Solution:

We have

normal vector =

\vec{n}=2\hat{i}-3\hat{j}+4\hat{k}

Unit vector to the plane ,

\begin{aligned} &\hat{n}=\frac{\vec{n}}{\left | \vec{n} \right |}\\ &=\frac{2\hat{i}-3\hat{j}+4\hat{k}}{\sqrt{(2)^2+(-3)^2+(4)^2}}\\ &=\frac{2\hat{i}-3\hat{j}+4\hat{k}}{\sqrt{4+9+16}}\\ &=\frac{2\hat{i}-3\hat{j}+4\hat{k}}{\sqrt{29}}\\ &\hat{n}=\frac{2}{\sqrt{29}}\hat{i}-\frac{3}{\sqrt{29}}\hat{j}+\frac{4}{\sqrt{29}}\hat{k} \end{aligned}

Equation of plane in normal form is

\begin{aligned} &\vec{r}.\hat{n}=d\\ &\text { Put }\hat{n}=\frac{2}{\sqrt{29}}\hat{i}-\frac{3}{\sqrt{29}}\hat{j}+\frac{4}{\sqrt{29}}\hat{k}\text { and }d=\frac{6}{\sqrt{29}}\\ &\vec{r} \left ( \frac{2}{\sqrt{29}}\hat{i}-\frac{3}{\sqrt{29}}\hat{j}+\frac{4}{\sqrt{29}}\hat{k} \right ) =\frac{6}{\sqrt{29}}\\ \end{aligned}

This is the required vector equation.

For finding Cartesian form

Put

\begin{aligned} &\vec{r}=\left ( x\hat{i}+y\hat{j}+z\hat{k} \right )\\ &\left ( x\hat{i}+y\hat{j}+z\hat{k} \right ) \left ( \frac{2}{\sqrt{29}}\hat{i}-\frac{3}{\sqrt{29}}\hat{j}+\frac{4}{\sqrt{29}}\hat{k} \right ) =\frac{6}{\sqrt{29}}\\ &\frac{2x-3y+4z}{\sqrt{29}}=\frac{6}{\sqrt{29}}\\ &2x-3y+4z=\frac{6(\sqrt{29})}{\sqrt{29}}\\ &2x-3y+4z=6 \end{aligned}

 

 

Posted by

Gurleen Kaur

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