Trigonometric-Identities Question 394
Question: $ 2\cos x-\cos 3x-\cos 5x= $
[Roorkee 1974]
Options:
A) $ 16{{\cos }^{3}}x{{\sin }^{2}}x $
B) $ 16{{\sin }^{3}}x{{\cos }^{2}}x $
C) $ 4{{\cos }^{3}}x{{\sin }^{2}}x $
D) $ 4{{\sin }^{3}}x{{\cos }^{2}}x $
Show Answer
Answer:
Correct Answer: A
Solution:
$ 2,\cos x-\cos ,3x-\cos ,5x=2\cos x(1-\cos 4x) $ $ =2\cos x,2{{\sin }^{2}}2x $ $ =4,\cos x,{{\sin }^{2}},2x=16,{{\sin }^{2}}x,{{\cos }^{3}}x $ .
BETA
