geometry chp 1

acute angle

An angle that has a measure greater than 0° and less than 90°.

adjacent angles

Two angles that share a common vertex and side, but have no common interior points.

angle

A set of points consisting of two different rays that have the same endpoint.

angle bisector

A ray that divides an angle into two congruent angles.

axiom

A rule that is accepted without proof.

between

When three points are collinear, one point is between the other two.

collinear points

Points that lie on the same line.

complementary angles

Two angles whose measures have a sum of 90°.

congruent angles

Two angles that have the same measure.

congruent segments

Line segments that have the same length.

construction

A geometric drawing that uses a limited set of tools, usually a compass and straightedge.

coordinate

A real number that corresponds to a point on a line.

coplanar points

Points that lie in the same plane.

defined terms

Terms that can be described using known words, such as point or line.

distance

The absolute value of the difference of two coordinates on a line.

endpoints

Points that represent the ends of a line segment or ray.

exterior of an angle

The region that contains all the points outside of an angle.

interior of an angle

The region that contains all the points between the sides of an angle.

intersection

The set of points two or more geometric figures have in common.

line

A line has one dimension, is represented with two arrowheads, and extends without end.

line segment

Consists of two endpoints and all the points between them.

linear pair

Two adjacent angles whose noncommon sides are opposite rays.

measure of an angle

The absolute value of the difference between the real numbers matched with the two rays that form the angle on a protractor.

midpoint

The point that divides a segment into two congruent segments.

obtuse angle

An angle that has a measure greater than 90° and less than 180°.

opposite rays

Two rays that share an endpoint and extend in opposite directions.

plane

A flat surface made up of points that has two dimensions and extends without end.

point

A location in space represented by a dot and has no dimension.

postulate

A rule that is accepted without proof.

ray

A part of a line that has one endpoint and extends forever in one direction.

right angle

An angle that has a measure of 90°.

segment

Consists of two endpoints and all the points between them.

segment bisector

A point, ray, line, segment, or plane that intersects a segment at its midpoint.

sides of an angle

The rays of an angle.

straight angle

An angle that has a measure of 180°.

supplementary angles

Two angles whose measures have a sum of 180°.

undefined terms

Words that do not have formal definitions, but there is agreement about what they mean.

vertex of an angle

The common endpoint of the two rays that form an angle.

vertical angles

Two angles whose sides form two pairs of opposite rays.