ACT Preparation / Unit 13 ACT 1202 short lesson, about 20 seconds
Complementary and Supplementary Angles
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The idea
Two angles are complementary when they add to 90° and supplementary when they add to 180°. Angles forming a straight line are supplementary.
In practice
The complement of 35° is 90 − 35 = 55°; its supplement is 180 − 35 = 145°.
Where people slip
Complementary goes with the corner, 90°; supplementary with the straight line, 180°.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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