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# geometry chapter 1

### chaoter 1 only

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

point | A dot in a specific location with no dimension |

line | A straight path with no thickness that continues in both directions |

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

line segment | portion of a line consisting of 2 points |

ray | a portion of a line that starts at a point and continues forever in 1 direction |

parallel | Lines that lie on the same plane but do not intersect |

coplaner | Points that lie on the same plane |

collinear | Points that lie on the same line |

postulate | a statement that is accepted as true without proof |

segment addition postulate | if B is between A and C then AB+BC = AC |

distance formula | (x2-x1)2+(y2-y1)2 |

midpoint | The point that divides the line segment into two segments that have the same length |

segment bisector | A line, ray, or other figure that passes through the midpoint of a segment |

angle | figure formed by 2 rays with the same endpoint |

vertex | common end point |

rays of angle | side of the angle |

degrees | common measurement for circular arcs |

right angle | 0<m<A<90 |

acute angle | m<A=90 |

obtuse angle | 90 <m<A<180 |

straight angle | m<A = 180 |

angle bisector | a ray that divided an angle into two angles that both have the same measure |

angle addition postulate | if S is interior of <PQR then m<PQR=m<PQS + m< SQR |

transformation | a function that changes the position shape and/or size of a figure |

preimage | A figure that is used as the input of a transformation |

image | The output |

rigid motion | a transformation that changes the position of a figure witnout changing the size or shape of the figure |

conjecture | a statement that is believed to be true |

Inductive reasoning | The process of reasoning a rule or statement may be true by looking at specific cases |

deductive reasoning | the process of using logic to prove whether all cases are true |

theorem | A statement that you can prove is true using a series of logical steps |

counterexample | an example that shows a conjecture to be false |

conditional statement | a statement that can be written in the form "if p then q" where p is hypothesis and q is the conclusion |

linear pair | A pair of adjacent angles whose non common sides are opposite rays. |

addition property | if a=b then a + c = b + c |

subtraction property | if a = b then a - c = b - c |

multi property | if a = b then ac = bc |

division property | if a = b and c = 0 then a/c = b/c |

Reflexive property | a = a |

Symmetric property | If a = b then b = a |

transitive property | if a = b and b = c then a = c |

substitution property | if a = b then b can be substituted for a in any expression |

The linear Pair Theorem | if two angles form a linear pair then they are supplementary m<3 + m<4 = 180 |