Trigonometric Identities Question 128
Question: If $ \tan A=\frac{1}{2},\tan B=\frac{1}{3}, $ then $ \cos 2A= $
[CET 1989]
Options:
A) $ \sin B $
B) $ \sin 2B $
C) $ \sin 3B $
D) None of these
Show Answer
Answer:
Correct Answer: B
Solution:
$ A+B=45{}^\circ , $ therefore $ 2A=90{}^\circ -2B $
$ \therefore \cos 2A=\sin 2B $ .