Complementary & Supplementary Angles

Two angles summing to 90° are complementary; summing to 180° are supplementary

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About This Practice

If two angles add up to 90° (a right angle), they are complementary; if they add up to 180° (a straight angle), they are supplementary. To find a complement subtract from 90°, to find a supplement subtract from 180°. The animation sweeps β into place, and the moment the right or straight angle fills up, the "sum" idea becomes visible.

Watch two angles combine into a right or straight angle: given angle α, pick its complement or supplement from three options, then watch the β-sweep animation fill the angle to see that everything is about the sum.

EasyEstimated Time: 15mincomplementary anglessupplementary anglesanglesright anglestraight angle

How to Play

  1. Choose the mode: complement (fill 90°) or supplement (fill 180°).
  2. Read the given angle α and decide whether to subtract from 90° or 180°.
  3. Compute mentally, then pick one of the three options.
  4. After a correct answer, watch the β-sweep animation verify the fill.
  5. Take a new problem: compute first, confirm with the animation.

Learning Objectives

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