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Provide solution for RD Sharma maths class 12 chapter 28 The Plane exercise multiple choice question 22

Answers (1)

Answer:

 Option (d)

Hint:

 Find the angle with vector dot product.

Given:

 \frac{x-2}{3}=\frac{y-3}{4}=\frac{z-4}{5}

Solution:

Given line

\frac{x-2}{3}=\frac{y-3}{4}=\frac{z-4}{5}

is parallel to the vector

\overrightarrow{b}=3\widehat{i}+4\widehat{j}+5\widehat{k}

Equation to the plane is 

2x - 2y + z = 5

Normal to the plane is

\overrightarrow{n}=2\widehat{i}-2\widehat{j}+\widehat{k}

If angle between line and plane is \theta

Then

\begin{aligned} &sin\theta =\frac{\left | \overrightarrow{b}.\overrightarrow{n} \right |}{\left | \overrightarrow{b} \right |.\left | \overrightarrow{n} \right |}\\ &=\frac{\left | (3\widehat{i}+4\widehat{j}+5\widehat{k}).(2\widehat{i}-2\widehat{j}+\widehat{k}) \right |}{\sqrt{3^2+4^2+5^2.\sqrt{4+4+1}}}\\ &=\frac{\left | 6-8+5 \right |}{\sqrt{50}.\sqrt{9}}\\ &=\frac{3}{15\sqrt{3}}\\ &=\frac{1}{5\sqrt{3}}\\ &\therefore sin\theta =\frac{\sqrt{2}}{10} \end{aligned}

Posted by

Gurleen Kaur

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