Get smart curated videos delivered to your inbox.   SUBSCRIBE

# How to find unknown angles

Watch more with these video collections:

Specific geometric characteristics define angles, and understanding their distinctions is essential in geometry. For instance, certain angles combine to create a right angle, while others form a straight line. Some angles share a side, and those created by intersecting lines are positioned opposite each other as vertical angles.

This Math Shorts video, created by Planet Nutshell for PBS Learning Media, demonstrates different angles—complementary, supplementary, adjacent, and vertical—and then shares how to find unknown angles by identifying what type of angle you’re looking at. Complementary Angles (Sum to 90°): In a right angle, subtract the known angle from 90 degrees to determine the unknown complementary angle.

Supplementary Angles (Sum to 180°): When two angles form a straight line, subtract the known angle from 180 degrees to find the unknown supplementary angle.

Adjacent Angles (shown above in orange): Assess the angle and its relationship with its neighbor; since adjacent angles add up to the larger angle, angle addition will determine the unknown adjacent angle.

Vertical Angles (Always Equal): Identify the known angle when lines intersect; pairs of angles opposite each other are always equal. Watch these related geometry videos next:
Angle Dance, a 80s-style music video by Plane Geometry
Observing the angle of repose with DIY physics devices
Michael Moschen’s The Triangle
• How many ways are there to prove the Pythagorean theorem?

This video was posted 2 weeks ago.