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

Answers (1)

Answer:  Proved

Hint:  You must know the rules of solving vectors

Given:  Show that the point whose position vectors are,

\vec{a}=4\hat{i}-3\hat{j}+\hat{k}, \ \ \ \vec{b}=2\hat{i}-4\hat{j}+5\hat{k}, \ \ \ \ \ \vec{c}=\hat{i}-\hat{j} from a right triangle.

Solution: Given that,

\begin{aligned} &\vec{a}=\overrightarrow{O A} \Rightarrow 4 \hat{\imath}-3 \hat{\jmath}+\hat{k} \\ &\vec{b}=\overrightarrow{O B} \Rightarrow 2 \hat{\imath}-4 \hat{\jmath}+5 \hat{k} \\ \end{aligned}

                                                                        \begin{aligned} &\qquad \vec{c}=\overrightarrow{O C} \Rightarrow \hat{\imath}-\hat{\jmath} \\ \end{aligned}

\begin{aligned} &\overrightarrow{A B}=\overrightarrow{O B}-\overrightarrow{O A} \Rightarrow-2 \hat{\imath}-\hat{\jmath}+4 \hat{k} \\ \end{aligned}

\begin{aligned} &\overrightarrow{B C}=\overrightarrow{O C}-\overrightarrow{O B} \Rightarrow-\hat{\imath}+3 \hat{\jmath}-5 \hat{k} \\\\ &\overrightarrow{C A}=\overrightarrow{O A}-\overrightarrow{O C} \Rightarrow 3 \hat{\imath}-2 \hat{\jmath}+\hat{k} \\ \end{aligned}

\begin{aligned} &\overrightarrow{A B} \cdot \overrightarrow{B C}=2-3-20 \Rightarrow-21 \neq 0 \\ &\overrightarrow{B C} \cdot \overrightarrow{C A}=-3-6-5 \Rightarrow-14 \neq 0 \\ &\overrightarrow{A B} \cdot \overrightarrow{C A}=-6+2+4 \Rightarrow 0 \end{aligned}

So, \overrightarrow{AB} is perpendicular to \overrightarrow{CA}

So, \Delta ABCis a right angle triangle.

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infoexpert21

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