Complex Numbers And Quadratic Equations question 303

Question: $ \cos (x+iy) $ is equal to [RPET 2001]

Options:

A) $ \sin x\cosh y+i\cos x\sinh y $

B) $ \cos x\cosh y+i\sin x\sinh y $

C) $ \cos x\cosh y-i\sin x\sinh y $

D) None of these

Show Answer

Answer:

Correct Answer: C

Solution:

It is obvious.