Question

Find the general solution for cos x = 0, where n is an integer.

Answer 1

first we solve this equation:
x = cos^-1(0) = pi/2 and 3pi/2

Now, this is the answer for angles between 0 and 2pi

but there are "negative angles" and angles larger than 2pi
so the general solution that includes all of these cases is:

x = pi/2 + n*pi

here n is any integer.