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Need Solution for R.D.Sharma Maths Class 12 Chapter 23 Scalar or Dot  Products  Exercise 23.1 Question 19 Maths Textbook Solution.

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Answer: proved

Hint: you must know the rules of solving vectors

Given: \vec{b}=\hat{i}-3\hat{j}+5\hat{k},

\vec{c}=2\hat{i}+\hat{j}-4\hat{k}, form a right angle

Solution: Let ABC be the given triangle

\begin{aligned} &\overrightarrow{A C}=\vec{b}=\hat{\imath}-3 \hat{\jmath}+5 \hat{k} \\ &\overrightarrow{C B}=\vec{a}=3 \hat{\imath}-2 \hat{\jmath}+\hat{k} \\ &\overrightarrow{A B}=\vec{c}=2 \hat{\imath}+\hat{\jmath}-4 \hat{k} \\ &\vec{a} \cdot \vec{b}=3+6+5=14 \\ &\vec{b} \cdot \vec{c}=2-3-20=-21 \\ &\vec{a} \cdot \vec{c}=6-2-4=0\\&\operatorname{So} \overrightarrow{A B} \text { is } \perp \text { to } \overrightarrow{CB} \end{aligned}                                                \mid \therefore \Delta ABC \text{is a right angle triangle} \mid

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