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# Polygons Vocabulary

### Polygons

Question | Answer |
---|---|

acute triangle | A triangle with all angles measures less than 90 degrees. |

isosceles triangle | A triangle with at least two congruent sides; two side lengths are the same. |

right triangle | A triangle with one 90 degree angle. |

scalene triangle | A triangle that has NO congruent sides; all side lengths are different. |

equilateral triangle | A triangle with three congruent sides; all side lengths have the same measure. |

obtuse | A triangle with one obtuse angle; one angle measure is greater than 90 degrees. |

triangle | A three sided polygon. |

triangle sum theorem | The theorem which states that the angles measures of any triangle must have a sum of 180 degrees; the angles of a triangle add up to 180 degrees. |

leg | In a right triangle, the legs are the two sides which create the right angle; the perpendicular line segments. |

hypotenuse | In a right triangle, the side opposite the right angle; the longest side in a right triangle. The side of the triangle that is does not create the right angle. |

triangle inequality | The rule that says the smallest side length plus the medium side length must have a sum greater than the largest side length. Small + Medium > Large |

3 sided shape | triangle |

4 sided shape | quadrilateral |

5 sided shape | pentagon |

6 sided shape | hexagon |

7 sided shape | septagon or heptagon |

8 sided shape | octagon |

9 sided shape | nonagon |

10 sided shape | decagon |

11 sided shape | hendecagon or an 11-gon |

12 sided shape | dodecagon |

15 sided shape | pentadecagon |

Sum of the interior angles of a polygon | (n-2) x 180 where n is the number of sides on the polygon |

Number of triangles formed when a polygon is divided into triangles using diagonals (triangulation) | n-2 (n is the number of sides) |

The measure of each interior angle of a regular polygon | Sum of the interior angles / number of sides |

Triangulate or Triangulation | The process of dividing a polygon into triangles by drawing its diagonals |

Polygon | A closed plane figure created by three or more line segments that intersect only at their endpoints (vertices) |

Regular Polygon | A polygon with congruent sides and angles |

Congruent | Having the same size and shape |