Supplementary angles
Two angles whose sum is 180 degrees
Supplementary angles are two angles that add up to 180 degrees. In other words, if we have two angles A and B, and if A + B = 180 degrees, then A and B are said to be supplementary angles.
For example, if angle A measures 120 degrees, then angle B (which is supplementary to A) would measure 60 degrees (i.e. 180 – 120 = 60). Similarly, if angle B measures 100 degrees, then angle A (which is supplementary to B) would measure 80 degrees (i.e. 180 – 100 = 80).
It is worth noting that when two angles are supplementary, they form a straight line. In other words, they are adjacent angles that together form a straight angle. Therefore, if we know one of the angles, we can easily find the other by subtracting it from 180 degrees.
Finally, it is important to remember that two angles can only be supplementary if they both lie on the same plane (i.e. they are not vertical angles). Also, two angles that add up to 90 degrees are called complementary angles, not supplementary angles.
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