Question

Question #4207d

Answer 1

`x=pi/2+npi` for `n=0,\pm 1,\pm 2, \pm 3,...`

Explanation:

I assume you mean `cos(2x)+1=0`. This is equivalent to `cos(2x)=-1`. The cosine function will equal `-1` whenever its input is `pi` (radians) plus or minus some integer multiple of `2pi` (radians).

In this case, that means `2x=pi+2npi` for `n=0,\pm 1,\pm 2, \pm 3,...`

Dividing everything by 2 gives `x=pi/2+npi` for `n=0,\pm 1,\pm 2, \pm 3,...`