A) 1/2
B) 5/4
C) \[SinA\sin B\]
D) \[\cos A\cos B\]
Correct Answer: A
Solution :
\[\cos A=\cos B\cos C\]and \[A+B+C=\pi \] or \[B+C=\pi -A\] \[\Rightarrow \] \[\cos (B+C)=\pi -A\] \[\cos B\cos C-\sin B\sin C=\cos B\cos C\] \[2\cos B\cos C=\sin B\sin C\] \[\frac{\cos B\cos C}{\sin B\sin C}=1/2\Rightarrow \cot B\cot C=1/2\]You need to login to perform this action.
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