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Need Solution for R.D.Sharma Maths Class 12 Chapter 23 Scalar or Dot  Products  Exercise 23 .1 Question 25 Maths Textbook Solution.

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Answer:  Proved

Hint:  You must know the rules of solving vectors.

Given:  If  A, B and C have position vectors \left ( 0,1,1, \right ) \left ( 3,1,5 \right ) and \left ( 0,3,3 \right ) respectively. Show \Delta ABCright angled at C.

Solution: Given that,

\begin{aligned} &\overrightarrow{O A}=0 \hat{\imath}+\hat{\jmath}+\hat{k} \\ &\overrightarrow{O B}=3 \hat{\imath}+1 \hat{\jmath}+5 \hat{k} \\ &\overrightarrow{O C}=0 \hat{\imath}+3 \hat{\jmath}+3 \hat{k} \\ \end{aligned}

\begin{aligned} &\overrightarrow{B C}=\overrightarrow{O C}-\overrightarrow{O B} \\ &\overrightarrow{B C}=-3 \hat{\imath}+2 \hat{\jmath}-2 \hat{k} \\ &\overrightarrow{C A}=\overrightarrow{O A}-\overrightarrow{O C} \\ &\overrightarrow{C A}=0 \hat{\imath}-2 \hat{\jmath}-2 \hat{k} \end{aligned}

Now,

\begin{aligned} &\overrightarrow{B C} \cdot \overrightarrow{C A}=0-4+4 \\ &\overrightarrow{B C} \cdot \overrightarrow{C A}=0 \end{aligned}

So, \overrightarrow{BC} is perpendicular to .\overrightarrow{CA}

So, \Delta ABCis right angled at C.

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