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Provide solution for RD Sharma Maths Class 12 Chapter 25 Scale Triple Product Exercise Very Short Answer Question, question 3.

Answers (1)

Answer:

0

Hint:

Use scalar triple product formula.

Given:

\left[\begin{array}{lll} \hat{i}-\hat{j} & \hat{j}-\hat{k} & \hat{k}-\hat{i} \end{array}\right]

Solution:

\left[\begin{array}{lll} \hat{i}-\hat{j} & \hat{j}-\hat{k} & \hat{k}-\hat{i} \end{array}\right]

\begin{aligned} &=(\hat{i}-\hat{j}) \cdot\{(\hat{j}-\hat{k}) \times(\hat{k}-\hat{i})\} \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \quad[\because[\overrightarrow{\boldsymbol{a}} \overrightarrow{\mathbf{b}} \overrightarrow{\mathbf{c}}]=\overrightarrow{\boldsymbol{a}} \cdot(\overrightarrow{\boldsymbol{b}} \times \overrightarrow{\boldsymbol{c}})] \\ &=(\hat{i}-\hat{j}) \cdot((\hat{j} \times \hat{k})-(\hat{j} \times \hat{i})-(\hat{k} \times \hat{k})+(\hat{k} \times \hat{i})\} \end{aligned}

\begin{aligned} &=(\hat{i}-\hat{j}) \cdot\{\hat{i}-(-\hat{k})-0+\hat{j}\} \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \quad\left[\begin{array}{l} \because \hat{\jmath} \times \widehat{\boldsymbol{k}}=\hat{\boldsymbol{k}}, \hat{\boldsymbol{j}} \times \hat{\boldsymbol{\imath}}=-\widehat{\boldsymbol{k}} \\ \widehat{\boldsymbol{k}} \times \hat{\boldsymbol{i}}=\hat{\boldsymbol{j}}, \widehat{\boldsymbol{k}} \times \widehat{\boldsymbol{k}}=\mathbf{0} \end{array}\right] \\ &=(\hat{i}-\hat{j}) \cdot(\hat{i}+\hat{j}+\hat{k}) \\ &=(\hat{i} \hat{i})+(\hat{i} \cdot \hat{j})+(\hat{i} \cdot \hat{k})-(\hat{j} \hat{i})-(\hat{j} . \hat{j})-(\hat{j} \cdot \hat{k}) \end{aligned}

\begin{aligned} &=1+0+0-0-1-0\; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; &\left[\begin{array}{l} \because \hat{\imath} . \hat{\jmath}=\hat{\imath} . \hat{\boldsymbol{k}}=\hat{\jmath} \cdot \hat{\boldsymbol{i}}=\hat{\boldsymbol{j}} \cdot \hat{\boldsymbol{k}}=0 \\ \hat{\boldsymbol{\imath}} \cdot \hat{\boldsymbol{i}}=\hat{\boldsymbol{\jmath}} \cdot \hat{\boldsymbol{j}}=\mathbf{1} \end{array}\right] \end{aligned}

=1-1=0

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