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Need Solution for R.D.Sharma Maths Class 12 Chapter 23 Scalar or Dot  Products Exercise 23.1 Question 37 Maths Textbook Solution.

Answers (1)

Answer:  -\hat{i}-\hat{j}-\hat{k},7\hat{i}-2\hat{j}-5\hat{k}

Hint: You must know the rules of solving vectors.

Given: Decompose the vector 6\hat{i}-3\hat{j}-6\hat{k} into vector which are parallel and perpendicular to the vector \hat{i}+\hat{j}+\hat{k}

Solution:

Let \vec{a}=6\hat{i}-3\hat{j}-6\hat{k}

\vec{b}=\hat{i}+\hat{j}+\hat{k}

And \vec{x} and \vec{y}  be such that,

                                        \Rightarrow \vec{a}=\vec{x}+\vec{y}

\Rightarrow \vec{y}=\vec{a}-\vec{x}

Since  \vec{x} is parallel to \vec{b}

\begin{aligned} &\Rightarrow \vec{x}=t \vec{b} \\ &\Rightarrow \vec{x}=t(\hat{\imath}+\hat{\jmath}+\hat{k}) \\ &\Rightarrow \vec{x}=t \hat{\imath}+t \hat{\jmath}+t \hat{k} \end{aligned}

Substituting the values of \vec{x} and  \vec{a}

\begin{aligned} &\vec{y}=(6 \hat{i}-3 \hat{\jmath}-6 \hat{k})-(t \hat{\imath}+t \hat{\jmath}+t \hat{k}) \\ &\vec{y}=(6-t) \hat{\imath}+(-3-t) \hat{\jmath}+(-6-t) \hat{k} \end{aligned}

Since y is perpendicular to \vec{b}

\begin{aligned} &\Rightarrow \vec{y} \cdot \vec{b}=0 \\ &\Rightarrow[(6-t) \hat{\imath}+(-3-t) \hat{\jmath}+(-6-t) \hat{k}] \cdot(\hat{\imath}+\hat{\jmath}+\hat{k})=0 \\ &\Rightarrow 1(6-t)+1(-3-t)+1(-6-t)=0 \\ \end{aligned}

\begin{aligned} &\Rightarrow-3-3 t=0 \\ &\Rightarrow t=-1 \\ &\vec{x}=-\hat{\imath}-\hat{\jmath}-\hat{k} \\ &\vec{y}=7 \hat{\imath}-2 \hat{\jmath}-5 \hat{k} \end{aligned}

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