Can someone help me with this problems?

Simplify

1. (cos^2 (pi/2 - x))/cos x. I have no idea how to solve this one

2. tan^2 x /sec^2 x . Could this one be -1/sec^2 x ?

3. 1/(tan^2 x + 1)

4. tan x - (sec^2 x )/ tan x. I have -1/tan x

Thanks!

Isabel