Complementary Angles
Two angles alpha and beta are said to be complementary if alpha+beta=pi/2. In other words, alpha and beta are complementary angles if they produce a right angle when combined.
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Angle, Right Angle, Supplementary Angles Explore this topic in the MathWorld classroomExplore with Wolfram|Alpha
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Weisstein, Eric W. "Complementary Angles." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/ComplementaryAngles.html