The Lesson
Explementary angles are two angles which add up to a full angle (360°).
A Real Example of Explementary Angles
Angles of 240° and 120° are explementary angles.
240° + 120° = 360°

How to Find an Explementary Angle
Question
What is the missing angle θ below?
Step-by-Step:
1
The 160° angle and θ are explementary angles.
160° + θ = 360°
2
Subtract the 160° angle from 360°.
θ = 360° − 160° = 200°