Hello, first time posting.

Had a quick question on a problem I was doing.

The problem:

Find exact solutions

$\displaystyle \cos x = \cot x$

What I've done so far is

$\displaystyle \cos x = \cot x$

$\displaystyle \cos x = (\cos x / \sin x)$

$\displaystyle \sin x = \cos x / \cos x )$

$\displaystyle \sin x = 1$

Now, when $\displaystyle \sin x = 1$ then x is $\displaystyle \pi / 2$. But the answer is also $\displaystyle 3 \pi / 2$

But isn't $\displaystyle 3 \pi / 2 = -1$?

I'm missing a part of the theory obviously, was just wondering if someone could clarify.

Thank you!