Trigonometric Identities Question 201
Question: .If $ \cos A=\frac{3}{4} $ , then $ 32\sin \frac{A}{2}\cos \frac{5}{2}A= $
[EAMCET 1982]
Options:
A) $ \sqrt{7} $
B) $ -\sqrt{7} $
C) 7
D) -7
Show Answer
Answer:
Correct Answer: B
Solution:
$ \cos A=\frac{3}{4}\Rightarrow \sin A=\frac{\sqrt{7}}{4} $ L.H.S $ =16(\sin 3A-\sin 2A) $ $ =16\sin A(3-4{{\sin }^{2}}A-2\cos A) $ $ =16.\frac{\sqrt{7}}{4}( 3-4.\frac{7}{16}-2.\frac{3}{4} )=-\sqrt{7} $ .
BETA
