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Provide solution for RD Sharma maths class 12 chapter 27 Straight Line in Space exercise 27.1 question 11 maths textbook solution

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Answer :-

\frac{-2}{7}, \frac{6}{7},-\frac{3}{7} ; \vec{r}=(4 \hat{\imath}+\hat{k})+\lambda(-2 \hat{\imath}+6 \hat{\jmath}-3 \hat{k})

Hint :-

\vec{r}=x \hat{\imath}-y \hat{\jmath}+z \hat{k}

Given :-

\frac{4-x}{2}=\frac{y}{6}=\frac{1-z}{3}

Solution :-

\begin{aligned} & \frac{4-x}{2}=\frac{y}{6}=\frac{1-z}{3} \\ \Rightarrow & \frac{x-4}{-2}=\frac{y}{6}=\frac{z-1}{-3} \end{aligned}      

Direction ratios are (-2 , 6 , -3)

So, its directional cosines will be

\frac{-2}{\sqrt{(-2)^{2}+6^{2}+(-3)^{2}}}, \frac{6}{\sqrt{(-2)^{2}+6^{2}+(-3)^{2}}}, \frac{-3}{\sqrt{(-2)^{2}+6^{2}+(-3)^{2}}} \\
=\frac{-2}{7}, \frac{6}{7},-\frac{3}{7}

Let \frac{x-4}{-2}=\frac{y}{6}=\frac{z-1}{-3}=\lambda (say)

\Rightarrow x=-2 \lambda+4 \quad, \quad y=6 \lambda, \quad z=-3 \lambda+1

We know that

\vec{r}=x \hat{\imath}+y \hat{\jmath}+z \hat{k} \\

    =(-2 \lambda+4) \hat{\imath}+(6 \lambda) \hat{\jmath}+(-3 \lambda+1) \hat{k} \\

    =(4 \hat{\imath}+\hat{k})+\lambda(-2 \hat{\imath}+6 \hat{\jmath}-3 \hat{k})

                        Where ? is constant parameter.

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