Trigonometric Equations Question 387
Question: The general value $ \theta $ is obtained from the equation $ \cos 2\theta =\sin \alpha , $ is
[MP PET 1996]
Options:
A) $ 2\theta =\frac{\pi }{2}-\alpha $
B) $ \theta =2n\pi \pm ( \frac{\pi }{2}-\alpha ) $
C) $ \theta =\frac{n\pi +{{(-1)}^{n}}\alpha }{2} $
D) $ \theta =n\pi \pm ( \frac{\pi }{4}-\frac{\alpha }{2} ) $
Show Answer
Answer:
Correct Answer: D
Solution:
- $ \cos 2\theta =\cos ( \frac{\pi }{2}-\alpha )\Rightarrow 2\theta =2n\pi \pm ( \frac{\pi }{2}-\alpha ) $
$ \Rightarrow $ $ \theta =n\pi \pm ( \frac{\pi }{4}-\frac{\alpha }{2} ) $ .
BETA
