### Home > CCA2 > Chapter 8 > Lesson 8.1.1 > Problem8-16

8-16.

Without a calculator, find two solutions $0°\leθ<360°$ that make each of the following equations true.

1. $\cosθ=\frac{1}{2}$

Draw a unit circle.

The cosine is where the $x-$value (red line) is $\frac{1}{2}.$

Answers: 60° and 300°

1. $\tan θ = −1$

$135° \text{and}\ 315°$

1. $\sinθ=\frac{\sqrt{3}}{2}$

Draw and label a unit circle as in part (a). Don't forget that the sine is the y-value! Which quadrants will the angles be in?

1. $\cosθ=−\frac{\sqrt{3}}{2}$

See part (c).