# `cos(theta) = -sqrt(2)/2` Find two solutions of each equation. Give your answers in degrees (0 <= theta <= 360) and radians (0 <= theta <= 2pi)

### 3 Answers | Add Yours

Sine and cosine at max are 1. Cosine is X and Sine is Y. The values of them repeat as their graphs are waves. As you can see here

# So here `3pi/4` and `5pi/4` can both equal theta

theta can be 135 degrees or it can be 225 degrees

The above solution is right

this is the continuation

In

radians the

value of `theta = (3pi)/4 and (5pi)/4`

`cos(theta)` is negative in the 2nd and 3rd quadrants. Looking at a unit circle, the values of theta that satisfy this are 135 and 225 degrees.

**Sources:**