question_answer

Two forces \[{{\vec{F}}_{1}}=5\hat{i}+10\hat{j}-20\hat{k}\]and \[{{\vec{F}}_{2}}=10\hat{i}-5\hat{j}-15\hat{k}\] act on a single point. The angle between \[{{\vec{F}}_{1}}\]and \[{{\vec{F}}_{2}}\] is nearly                                      [AMU 1995]

A)                 \[\text{3}0{}^\circ \]      

B)                 \[\text{45}{}^\circ \]

C)                 \[\text{6}0{}^\circ \]      

D)                 \[\text{9}0{}^\circ \]