Chapter 12.1, Problem 21OE

To determine

Give two angles , one positive and one negative , that are coterminal with the given angle.

  $120°$

Answer to Problem 21OE

  $480°\text{ and }-240°$

Explanation of Solution

Given:

The angle is :

  $120°$

Formula Used:

Two angles in standard position are coterminal if their terminal sides coincide.

So, the measures of all angles coterminal with $\theta$ are:

  $\theta +n\cdot 360°$

where n is an integer.

Calculation:

The positive angle coterminal with $120°$ is $120°+360°=480°$

The negative angle coterminal with $120°$ is $120°-360°=-240°$