Trigonometric Identities Question 2
Question: $ 2\sin A{{\cos }^{3}}A-2{{\sin }^{3}}A\cos A= $
[Roorkee 1975; Kerala (Engg.) 2001]
Options:
A) $ \sin 4A $
B) $ \frac{1}{2}\sin 4A $
C) $ \frac{1}{4}\sin 4A $
D) None of these
Show Answer
Answer:
Correct Answer: B
Solution:
$ 2\sin A{{\cos }^{3}}A-2{{\sin }^{3}}A\cos A $ $ =2\sin A\cos A({{\cos }^{2}}A-{{\sin }^{2}}A) $ $ =2\sin A\cos A\cos 2A=\sin 2A\cos 2A=\frac{1}{2}\sin 4A $ .
BETA
