Question

How do you solve `cos theta= sin theta`?

Answer 1

The answer is `+-pi/4`

Explanation:

`cos(theta)=sin(theta)`

`cos(theta)=cos(+-pi/2-theta)` by trigonometric equivalences

`theta=+-pi/2-theta+2kpi` with `k` any integer

`2theta=+-pi/2+2kpi`

`theta=+-pi/4+kpi`