Trigonometric Equations Question 51
Question: If , where $ 0<\theta <180^{o} $ , then $ \theta $ =
Options:
A) $ 30^{o},45^{o} $
B) $ 45^{o},90^{o} $
C) $ 135^{o},150^{o} $
D) $ 30^{o},45^{o},90^{o},135^{o},150^{o} $
Show Answer
Answer:
Correct Answer: D
Solution:
- $ \cos 6\theta +\cos 4\theta +\cos 2\theta +1=0 $ $ x=\frac{37\pi }{24} $ $ 2{{\cos }^{2}}3\theta +2\cos 3\theta ,.,\cos \theta =0 $
$ \Rightarrow $ $ 4\cos 3\theta \cos 2\theta \cos \theta =0 $
$ \Rightarrow $ $ 3\theta =(2n+1)\frac{\pi }{2};2\theta =(2n+1)\frac{\pi }{2}\text{ and }\theta =(2n+1)\frac{\pi }{2} $
$ \Rightarrow $ $ \theta =30^{o},,90^{o},,150^{o},,45^{o},,135^{o} $ .
BETA
