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# Geometry Chapter 2

### Polygons and Logical Statements

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

Polygon | An enclosed figure created by the union of line segments, where endpoints meet at vertices, and no line segments overlap. |

Convex Polygon | A polygon without indentations. Rubber band rule: the rubberband will touch all vertices and line segments of a convex polygon. |

Concave Polygon | A polygon with an indentation(s). Rubber band rule: the rubberband will not touch all vertices and line segments; there will be a diagonal outside of the polygon. |

Polygonal region | A shaded-in polygon, where all points in the polygon are part of the region. |

Intersection of two (or more) sets of data | The values in common, or the overlap, in two or more sets of data. |

Union of two (or more) sets of data | All values that are in each set and the intersection. |

The Null Set or Empty Set | If two sets of data do not have any values in the intersection, their intersection is the empty set { }. |

Antecedant | The hypothesis, the part of a conditional that follows the "if" part. |

Consequent | The conclusion, the part of a conditional that follows the "then" part. |

A conditional | An If-Then statement. |

An instance of the conditional | The "If P" and the "then Q" parts are both true in the conditional. |

Counterexample | Keeping the if-part "P" in a conditional the same, and changing the then part "Q" to be different. |

Converse | Switching the antecedant (if part) and consequent (then part) in a conditional. |

Biconditional | If P implies Q is true, and Q implies P is true, a biconditional can be created such that "P if and only if Q"; a double arrow is used for bi conditional notation. |

Scalene Triangle | A triangle where there are no congruent side lengths or angles. |

Isosceles Triangle | A triangle with at least two congruent side lengths, and at least two congruent angles. |

Equilateral Triangle | A triangle whose side lengths are all the same. |

Equiangular Triangle | A triangle whose angles are all the same measure. |

Is an Isosceles triangle equilateral? | No, only if the isosceles triangle has all three side lengths being the same. |

Is an equilateral triangle isosceles? | Yes! An equilateral triangle will always have at least two sides congruent. |

Triangle | 3 sided polygon |

Quadrilateral | 4 sided polygon |

Pentagon | 5 sided polygon |

Hexagon | 6 sided polygon |

Heptagon | 7 sided polygon |

Octagon | 8 sided polygon |

Nonagon | 9 sided polygon |

Decagon | 10 sided polygon |

Dodecagon | 12 sided polygon |

N-gon | A polygon with n number of sides. |

Triangle Inequality Postulate | In triangle ABC, AB + BC > AC. |

Conjecture | A hypothesis, an opinion, a stereotype. Conjectures are NOT ALWAYS true. |

Created by:
aliciaobermann