# How do you solve #2cos^2 theta + cos theta -1 = 0#?

##### 1 Answer

Sep 15, 2016

#### Explanation:

Solve the quadratic equation for cos t.

Since a - b + c = 0, use shortcut. The 2 real roots are:

cos t = -1 and

Use trig table of special arcs and unit circle -->

a. cos t = -1 -->

General answers:

b.

arc

General answers: