Constructing angles (video) | Khan Academy
https://www.khanacademy.org/math/cc-fourth-grade-math/imp-geometry-2/imp-measuring-angles/v/constructing-angles
WEBPositive angles are measured counterclockwise, starting at Quadrant 1 in the Coordinate plane. Negative angles are measured clockwise, so, for example, an angle of - 30 degrees would be the same size as an angle of + 30 degrees, but would lie in Quadrant 4 instead of Quadrant 1. Show more...
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