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Please Solve R.D.Sharma class 12 Chapter 23 Scaler or Dot Products  Exercise 23.1 Question 1 Sub Question 1 Maths Textbook Solution.

 

Answers (1)

Answer:  19

Hints: you must the properly of vectors.

Given:\vec{a}=\hat{i}-2\hat{j}+\hat{k} and \vec{b}=4\hat{i}-4\hat{j}+7\hat{k}             Find \vec{a}.\vec{b}

Solution:                                                                                                

\begin{aligned} &\vec{a}=\hat{\imath}-2 \hat{\jmath}+\hat{k} \\\\ &\vec{b}=4 \hat{\imath}-4 \hat{j}+7 \hat{k} \\\\ &\vec{a} \cdot \vec{b}=(\hat{\imath}-2 \hat{\jmath}+\hat{k})(4 \hat{\imath}-4 \hat{\jmath}+7 \hat{k}) \\ \end{aligned}                                                        \therefore\left|\begin{array}{l} \hat{\imath} \cdot \hat{i}=1 \\ \hat{\imath} \cdot \hat{\jmath}=0 \end{array}\right|

\begin{aligned} &=(4+8+7) \\\\ &=19 \end{aligned}

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