A) \[{{90}^{o}}\]
B) \[{{60}^{o}}\]
C) \[{{45}^{o}}\]
D) \[{{30}^{o}}\]
Correct Answer: A
Solution :
According to the given condition \[{{R}^{2}}={{P}^{2}}+{{Q}^{2}}+2PQ\cos \alpha \] and \[{{R}^{2}}={{P}^{2}}+{{Q}^{2}}-2PQ\cos \alpha \] \[\Rightarrow \] \[{{P}^{2}}+{{Q}^{2}}+2PQ\cos \alpha \] \[\Rightarrow \] \[4PQ\cos \alpha =0\] \[\Rightarrow \] \[\alpha ={{90}^{o}}\]You need to login to perform this action.
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