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2 Angles are Supplementary when they add up to 180 degrees.
Supplement comes from Latin supplere, to complete or “supply” what is needed.
These two angles (120° and 60°) are Supplementary Angles, because they add up to 180° and make a straight angle.
But the angles don’t have to be together.
These 2 angles are supplementary because 120° + 60° = 180°
When the two angles add to 180°, we say they “Supplement” each other.
Supplementary Vs Complementary
A related idea is Complementary Angles, they add up to 90°
How to remember which is which? Just think:
|“S” of Supplementary||stands for “Straight” (a straight line)|
|“C” of Complementary||stands for “Corner” (a Right Angle)|