### Home > A2C > Chapter 13 > Lesson 13.1.2 > Problem 13-31

13-31.

For each of the following equations, find the solutions that lie in the domain

For the equation to be true,

must . You can either draw a unit circle to find all possible solutions or solve the equation graphically.

In what quadrants is cos

negative? When does

? Picture a unit circle. At what angle is the adjacent side the same length as the hypotenuse?