### Home > PC > Chapter 4 > Lesson 4.2.1 > Problem4-71

4-71.

Find all values of $θ$ from $[0, 2\pi]$ where the following equations are true. Sketching a picture of the unit circle may help.

1. $\text{sin }θ =\frac { 1 } { 2 }$

$30\degree\text{ or }\frac{\pi}{6}$
$150\degree\text{ or }\frac{5\pi}{6}$

1. $\text{cos }θ = −\frac { 1 } { 2 }$

1. $\text{sin }θ = - \frac { \sqrt { 3 } } { 2 }$

What special angle(s) are involved?
What does the negative sign mean?

1. $\text{cos }θ = 0$

These angles are coterminal with the $y$-axis.