Supplementary Angles
Two Angles are Supplementary if they add up to 180 degrees.
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These two angles (140° and 40°) are Supplementary Angles, beacuse they add up to 180°.
Notice that together they make a straight angle.
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But the angles don't have to be together.
These two are supplementary because 60° + 120° = 180°
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If the two angles add to 180°, we say they "Supplement" each other.
Supplement comes from Latin supplere, to complete or "supply" what is needed. |
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Spelling: be careful, it is not "Supplimentary Angle" (with an "i") |
Note: A related idea is Complementary Angles, they add up to 90°
(How can you remember that Complementary is 90° and Supplementary is 180°? Luckily "C" comes before "S" in the alphabet and 90 comes before 180. That's what I do.)
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