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# H Geom chap 1 vocab

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

undefined | a figure that can't be defined (described) by using other figures Point, Line, Plane |

point | a location that has no size, represented as a dot |

line | a straight line that has no thickness and extends, both directions, to infinity (forever) |

plane | a flat surface that has no thickness and extends in all directions to infinity (forever) |

collinear | points that lie on the same line |

coplanar | points that lie on the same plane |

noncoplanar | points that do not lie on the same plane |

segment (line segment) | part of a line consisting of two points and all the points in between them |

endpoint | a point at one end of the segment or the starting point of a ray |

ray | a part of a line that starts at an endpoint and extends forever (infinity) in one direction |

opposite rays | two rays that share a common endpoint and form a line |

postulate (axiom) | a statement that is accepted as true without proof--describes geometric properties |

coordinate of a point | a pair of numbers that define it's exact location on a 2-dimensional plane---(x,y) |

distance | absolute value of the difference of the coordinates |

length | distance between A and B on a line, segment, or ray |

congruent segments | segments that have the same length |

construction | a way of creating a figure that is more precise--one way use a compass and straightedge |

between | 3 points lie on the same line (collinear), the point that lies in the middle of the other two |

midpoint | the point that divides a segment into two congruent segments |

bisects | divides into 2 equal pieces |

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

angle | a figure formed by two rays or sides, with a common endpoint |

vertex (vertices) | common endpoint(s) |

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

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

measure | find the size, amount, or degree of something using an instrument or device marked in a standard unit |

degree | unit of measure for a circle which represents 1/360th of the circle |

acute angle | angle that measures greater than 0* and less than 90* , so 0*-90* |

right angle | measures exactly 90* |

obtuse angle | angle that measures greater than 90* and less than 180* , so 90*-180* |

straight angle | 2 opposite rays that measure 180* |

congruent angles | angles that have the same measure |

angle bisector | a ray that divides an angle into 2 congruent angles |

adjacent angles | 2 angles in the same plane with a common vertex and a common side |

linear pair of angles | pair of adjacent angles whose noncommon sides are opposite rays (form a line) |

complementary angles | 2 angles whose measures have a sum of 90* |

supplementary angles | 2 angles whose measures have a sum of 180* |

vertical angles | 2 nonadjacent angles formed by 2 intersecting lines (angles directly across from each other) |

perimeter | the sum of all the side lengths of a figure |

area | number of nonoverlapping square units that exactly cover the figure |

base | any side of a triangle |

height | segment from a vertex that forms a right angle with a base (from a triangle) |

diameter | segment whose endpoints are on a circle and passes through the center of the circle |

radius | segment whose endpoints are on the circle and the center of the circle |

circumference | distance around the circle |

pi | ratio of a circle's circumference to its diameter (same for all circles--about 3.14 or 22/7) |

coordinate plane | plane that is divided into four regions by a horizontal line (x-axis) and a vertical line (y-axis) |

legs | 2 sides that form the right angle of a triangle |

hypotenuse | side across from the right angle of a triangle |

transformation | change in position, size, or shape of a figure--translation, dilation, reflection, rotation |

preimage | original figure-before a transformation |

image | figure after a transformation from an original |

reflection | transformation across a line (line of reflection) ---flip |

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

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

coordinate | a point that corresponds to one and only one number on the ruler |

Created by:
rachel schmelzer