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# 5th Grade EDM Unit 3

### Geometry Explorations

Term | Definition |
---|---|

acute angle | an angle with a measure less than 90 degrees |

obtuse angle | an angle with a measure between 90 and 180 degrees |

reflex angle | an angle with a measure between 180 and 360 degrees |

right angle | an angle with a measure of 90 degrees |

adjacent angles | two angles with a common side and vertex that do not overlap |

arc | a part of a circle between and including two endpoints on the circle; named by its endpoints |

pentagon | a 5-sided polygon |

regular polygon | a polygon in which all sides are the same length and all angles have the same measure |

center of a circle | the point in the plane of a circle equally distant from all points on the circle |

radius of a circle | a line segment from the center of a circle or sphere to any point on the circle or sphere; half of the diameter |

perimeter | the distance around the boundary of a 2-dimensional figure |

circumference | the perimeter of a cirlce |

diameter | a line segment that passes through the center of a circle or sphere and has endpoints on the circle or sphere |

equilateral triangle | a triangle with all three sides equal in length; all angles measure 60 degrees |

isosceles triangle | a triangle with at least two sides equal in length; angles opposite the congruent sides are congruent to each other |

scalene triangle | a triangle with sides of three different lengths and three different angles |

regular tessellation | a tessellation of one regular polygon |

tessellation | a pattern of shapes that covers a surface completely without overlaps or gaps |

vertical angles | the angles made by intersecting lines that do not share a common side; also called opposite angles; angles have equal measures |

straight angle | an angle with a measurement of 180 degrees |

congruent | figures having the same size and shape |