A) 7
B) 8
C) 11
D) None of these
Correct Answer: C
Solution :
\[32\sin \frac{A}{2}\sin \frac{5A}{2}=16(\cos 2A-\cos 3A)\] \[=16(2{{\cos }^{2}}A-1-4{{\cos }^{3}}A+3\cos A)\] \[=16\left( 2\times \frac{9}{16}-1-4\times \frac{27}{64}+3\times \frac{3}{4} \right)=11\].You need to login to perform this action.
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