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# Geometry

### Vocabulary

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

Geometry | the study of points, lines, angles, surfaces, and solids. |

Point | a location in space |

line | a collection of points that extend forever in the same direction |

line segment | part of a line, 2 endpoints |

ray | a line that has a beginning point but no end |

angle | two rays with the same endpoint |

vertex | the point where two rays meet |

plane | a flat surface that extends forever in all directions |

parallel lines | lines that are always the same distance apart |

intersecting lines | lines that cross in the same plane |

perpendicular lines | intersecting lines that cross and form four right angles |

acute angle | less than 90 degress |

right angle | 90 degrees |

obtuse angle | greater than 90 but less than 180 degrees |

straight angle | 180 degrees |

reflex angle | between 180 and 360 degrees |

supplementary angles | 2 angles that measure 180 degrees |

complementary angles | 2 angles that measure 90 degress |

polygon | a closed plane figure with 3 or more sides |

triangle | 3 sides |

quadrilateral | 4 sides |

pentagon | 5 sides |

hexagon | 6 sides |

heptagon | 7 sides |

octagon | 8 sides |

nonagon | 9 sides |

decagon | 10 sides |

dodecagon | 12 sides |

Right Triangle | one 90 degree angle |

Obtuse Triangle | one angle more than 90 degrees |

Acute Triangle | all angles are less than 90 degrees |

Scalene Triangle | no sides equal and no equal angles |

Isosceles Triangle | 2 sides equaland 2 equal angles |

Equilateral Triangle | 3 sides equal and 3 angles that are 60 degrees each |

Square | 4 equal sides and 4 right angles |

Rectangle | 4 right angles and the opposite sides are equal |

Rhombus | 4 equal sides and the opposite angles are equal |

Parallelogram | 2 pairs of equal and parallel sides |

Trapezoid | one pair of parallel sides and one pair of sides that are not parallel |

sum of the measure of the interior angles of triangle | 180 degrees |

Perimeter | shortest distance around the outside of a polygon |

Perimeter Formula | add up all the sides |

Area | number of square units needed to cover a surface |

Altitude | height of a polygon |

Area of a Square | base x height |

Area of a Rectangle | base x height |

Area of a Parallelogram | base x height |

Area of a Triangle | 1/2 base x height |

Area of a Trapezoid | 1/2 x h x(base 1 + base 2) |

Created by:
ppearson