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# Geometry Chapter 1 K

### Vocabulary

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

undefined term | a basic figure not defined in terms of other figures |

point | an undefined term in Geometry that has no size |

line | a set of points extending infinitely in two directions |

plane | a flat surface with no thickness that extends forever |

collinear | points on the same line |

coplanar | points on the same plane |

segment | part of a line with 2 endpoints |

endpoint | one end of a segment or the starting place for a ray |

ray | a set of points extending infinitely in 1 direction |

opposite rays | 2 rays with a common endpoint that form a line |

postulate | a statement accepted as true without proof |

coordinate | a point that corresponds to a number |

distance | the absolute value of the difference in the coordinates |

length | the distance between 2 points |

congruent segments | 2 segments with the same length |

construction | a way to creating a more precise figure, in Geometry we use a compass and straightedge |

between | B is between A and C if and only if they points are collinear and AB + BC = AC. |

midpoint | a point that divides a segment into 2 congruent parts |

bisect | to cut into 2 congruent parts |

segment bisector | any ray, segment, or line that intersects a segment at its midpoint |

angle | 2 rays that have a common endpoint |

vertex | the common endpoint shared by the 2 rays of an angle |

interior of an angle | the set of all points between the sides of an angle |

exterior of an angle | the set of all points outside an angle |

measure | the size of an angle, in degrees |

degree | 1/360 of a circle |

acute angle | an angle less than 90 degrees |

obtuse angle | an angle greater than 90 degrees |

right angle | an angle that measures exactly 90 degrees |

straight angle | an angle that measure 180 degrees |

congruent angles | 2 angles with the same measure |

angle bisector | any line, segment, or ray that divides an angle into 2 congruent parts |

adjacent angles | 2 angles that share a common side and vertex |

linear pair | 2 adjacent angles that form a straight line |

complementary angles | a pair of angles that have a sum of 90 degrees |

supplementary angles | a pair of angles that have a sum of 180 degrees |

vertical angles | 2 angles whose sides form opposite rays |

coordinate plane | a plane that is divided into 4 regions by a horizontal and vertical axis |

leg | the sides of a right triangle that form the right angle |

hypotenuse | the side of a right triangle that is opposite the right angle |

transformation | the change in the position, size, or shape of a figure |

preimage | the original figure in a transformation |

image | the new figure in a transformation |

reflection | (a flip) a transformation across a line called the line of reflection |

translation | (a slide)a transformation in which all the points of a figure move the same direction in the same distance |

rotation | (a turn)a transformation about a point P called a center of rotation |

Created by:
stacykeener