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Teachers & SchoolsStudy Guide

Not to be confused with angels, **angles **are the pointed corners of shapes. Angles can be named three different ways.

**This angle could be named any of these ways:**

- (counterclockwise)
- (clockwise)
- (just the vertex)

*Look Out**: when naming an angle using three letters, the vertex must always be the middle letter!*

Name | Description | Example |

Acute Angle | An angle less that 90°.
Lame joke: this angle is so small and a-cute! | |

Obtuse Angle | An angle greater than 90°, but less than 180°. | |

Right Angle | An angle that is exactly 90°.
This is commonly denoted with a small box in the corner. | |

Straight Angle | A 180° angle. It's - you guessed it - a straight line. | |

Supplementary Angles and Linear Pairs | Angles that add up to 180°. are supplementary angles. If the two angles are adjacent (next to each other) and add up to 180°, they are a linear pair. are also a linear pair. | |

Complementary Angles | Angles that add up to 90°.
are complementary. | |

Vertical Angles | When two lines intersect, opposite angles are called "vertical angles". Vertical angles are congruent. |

See the squiggly line over the equal sign above? This symbol means congruent. Oh, and btw, congruent angles have the same measurement.