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# Geometry -1

### AP Geometry Chapter 1 Definitions

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

Names a location and has no size. It is represented by a dot | Point |

A straight path that has no thickness and extends forever | Line |

A flat surface that has no thickness and extends forever | Plane |

Points that lie on the same line are | Collinear |

Points that lie on the same plane are | Coplanar |

The part of a line consisting of two points and all points between them. | Segment |

A point at one end of a segment or the starting point of a ray. | Endpoint |

A part of a line that starts at an endpoint and extends forever in one direction | Ray |

Two rays that have a common endpoint and form a line | Opposite Rays |

A statement that is accepted as true without proof | Postulate |

A point that corresponds to one and only one spot on a line | Coordinate |

The absolute value of the difference of the coordinates | Distance |

Another term for Distance | Length |

Segments that have the same length. | Congruent Segments |

A way to of creating a figure that is more precise | Construction |

The point that divides a segment into two congruent segments | Midpoint |

When given 3 points and all three points lie on the same line, one point can be said to be ___________ the other points. | Between |

To divide into congruent parts | Bisect |

A line, ray or segment that divides a segment into two congruent segments | Segment Bisector |

An angle that measures greater than 0° and less than 90° | Acute Angle |

A figure formed by 2 rays with a common endpoint | Angle |

A ray that divides an angle into two congruent angles | Angle bisector |

Angles that have the same measurement | Congruent angles |

A unit of angle measure and is 1/360 of a circle | Degree |

The set of all points outside an angle | Exterior of an angle |

The set of all points between the sides of an angle | Interior of an angle |

The difference of 360° and the measure of the associated minor arc | Measure of a major arc |

An angle that measures greater than 90° and less than 180° | Obtuse angle |

An angle that measures 90° | Right angle |

An angle formed by two opposite rays that measures 180° | Straight angle |

The common endpoint of the sides of the angle | Vertex of an angle |

Two angles in the same plane with a common vertex and a common side, but no common interior points | Adjacent angles |

Two angles whose measures have a sum of 90° | Complementary angles |

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

Two angles whose measures have a sum of 180° | Supplementary Angles |

The nonadjacent angles formed by two intersecting lines | Vertical angles |

The number of non-overlapping unit squares of a given size that will exactly cover the interior of a plane figures | Area |

Any side of a triangle | Base |

The distance around a circle | Circumference |

(The length of) A segment that passes through the center of a circle and whose endpoints are on the circle. | Diameter |

A segment from a vertex that forms a right angle with a line containing the base | Height of a triangle |

The sum of the side lengths of a closed plane figure | Perimeter |

The ratio of the circumference of a circle to it's diameter | pi |

a segment whose endpoints are the center of a circle and a point on the circle | Radius |

A plane that is divided into four regions by a horizontal line called the x-axis and a vertical line called the y-axis | Coordinate plane |

The side opposite the right angle in a right triangle | Hypotenuse |

One of the two sides of the right triangle that form the right angle | Leg |

A change in the position, shape or size of a figure. | Transformation |

a shape that RESULTS from a transformation of a figure known as a preimage | Image |

The original figure in a transformation | Preimage |

A transformation across a line, where each point and is image are the same distance for the line of reflection | Reflection |

A transformation about a point P where each point and it's image are the same distance from P | Rotation |

A transformation in which all the points of a figure move the same distance and same direction | Translation |