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  • Please Solve RD Sharma Class 12 Chapter 23 Scalar or Dot Product Exercise Very Short Answer Question 26 Maths Textbook Solution.

Please Solve RD Sharma Class 12 Chapter 23 Scalar or Dot Product Exercise Very Short Answer Question 26 Maths Textbook Solution.

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Answer :-   \cos ^{-1}\left(\frac{-1}{3}\right)

Hint :- You must know the formula of  \vec{a}\cdot \vec{b}

Given :-   \vec{a}=\hat{\imath}-\hat{\jmath}+\hat{k}\: \&\: \vec{b}=\hat{\imath}+\hat{\jmath}-\hat{k}

Solution :- we know that   \cos \theta=\frac{\vec{a} \cdot \vec{b}}{|\vec{a}||\vec{b}|}

\begin{aligned} &\Rightarrow \cos \theta=\frac{(\hat{\imath}-\hat{j}+\hat{k})(\hat{i}+\hat{j}-\hat{k})}{\sqrt{1+1+1} \sqrt{1+1+1}} \\ & \end{aligned}

\Rightarrow \cos \theta=\frac{1-1-1}{\sqrt{3} * \sqrt{3}} \\

\Rightarrow \cos \theta=\frac{-1}{3} \\

\Rightarrow \theta=\cos ^{-1}\left(\frac{-1}{3}\right)

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