A) zero
B) \[{{45}^{o}}\]
C) \[{{90}^{o}}\]
D) \[{{180}^{o}}\]
Correct Answer: C
Solution :
\[\vec{A}=3\hat{i}+4\hat{j}+5\hat{k},\vec{B}=3\hat{i}+4\hat{j}-5\hat{k}\] \[\vec{A}.\vec{B}=(3\hat{i}+4\hat{j}+5\hat{k}).(3\hat{i}+4\hat{j}-5\hat{k})\] \[|\vec{A}||\vec{B}|cos\theta =9+16-25=0\] \[|\vec{A}|\ne 0,|\vec{B}|\ne 0,\]hence, \[\cos \theta =0,\theta ={{90}^{o}}\]You need to login to perform this action.
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