Question

What are the real and imaginary parts of CosZ?

Answer 1

$\cos Z = \cos (x+iy) = \cos x \cos iy – \sin x \sin iy\\ = \cos x \cos h y – i \sin x \sin hy\\$

Here real part of $\cos Z$ is $cos x \cos h y$ and imaginary part of $\cos Z$

is $\sin x \sin hy\\$ .