A) \[\text{3}0{}^\circ \]
B) \[\text{45}{}^\circ \]
C) \[\text{6}0{}^\circ \]
D) \[\text{9}0{}^\circ \]
Correct Answer: B
Solution :
\[\cos \theta =\frac{\overrightarrow{{{F}_{1}}}.\overrightarrow{{{F}_{2}}}}{|{{F}_{1}}||{{F}_{2}}|}\] \[=\frac{(5\hat{i}+10\hat{j}-20\hat{k}).(10\hat{i}-5\hat{j}-15\hat{k})}{\sqrt{25+100+400}\sqrt{100+25+225}}\]\[=\frac{50-50+300}{\sqrt{525}\sqrt{350}}\] Þ \[\cos \theta =\frac{1}{\sqrt{2}}\]\[\therefore \] \[\theta =45{}^\circ \]You need to login to perform this action.
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