- Two angles are complementary when their measures add up to , supplementary when they add up to .
- When two lines cross, the angles facing each other across the crossing point are vertically opposite.
- When a line crosses two other lines, angles located in the same position at each crossing are corresponding angles; angles between the two lines on opposite sides of the crossing line are alternate angles.
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Mathematics · 术语表
什么是 Angle pairs?
又称: vertically opposite angles · alternate angles