51 terms

acute angle

A angle that measures greater than 0 degrees and is less than 90 degrees

adjacent angles

Two angles in the same plane with a common vertex and a common side, but not common interior points

angle

A figure formed by two rays with a common endpoint

angle bisector

A ray that divides an angle into two congruent angles

area

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

base

Any side of a triangle

bisect

To divide into two congruent parts

circumference

The distance around a circle

collinear

Points that lie on the same line

complementary angles

Two angles whose measures have a sum of 90 degrees

congruent angles

Angles that have the same measure

congruent segments

Two segments that have the same length

coordinate

A number used to identify the location of a point

coordinate plane

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

coplanar

Points that lie in the same plane

degree

A unit of angle measure

diameter

A segments that have endpoints on the circle and passes through the center of the circle; also the length of the segment

distance

The absolute value of the difference of the coordinates of the points

endpoint

A point at an end of a segment or the starting point of a ray

exterior of an angle

The set of points outside an angle

height

A segment from any vertex that forms a right angle with a line containing the base

hypotenuse

The side opposite the right angle in a right triangle

image

A shape that results from a transformation of a figure known as the preimage

interior of an angle

The set of all points between the sides of an angle

leg

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

length

The distance between the two endpoints of a segment

line

A undefined term in geometry, it has no thickness and extends forever

linear pair

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

midpoint

The point that divides a segment into two congruent segments

obtuse angle

An angle that measures greater than 90 degrees and less than 180 degrees

opposite rays

Two rays that have a common endpoint and form a line

perimeter

The sum of the side lengths of a closed plane figure

pi

The ratio of the circumference of a circle to its diameter

plane

An undefined term in geometry, it is a flat surface that have no thickness and extends forever

point

An undefined term in geometry, it names a location and has no size

postulate

A statement that is accepted as true without proof

preimage

The original figure in a transformation

radius

A segment whose endpoints are the center of a circle and a point on the circle; the distance from the center of a circle to any point on the circle

ray

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

reflection

A transformation across a line, called the line of reflection

right angle

An angle that measures 90 degrees

rotation

A transformation about a point P, also known as the center of rotation, such that each point and its image are the same distance from P

segment

A part of a line consisting of two endpoints and all points between them

segment bisector

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

straight angle

An angle that measures 180 degrees

supplementary angles

Two angles whose measures have a sum of 180 degrees

transformation

A change in the position, size, or shape of a figure or graph

translation

A transformation that shifts or slides every point of a figure or graph the same distance in the same direction

undefined term

A basic figure that is not defined in terms of other figures

vertex

The common endpoint of the sides of the angle

vertical angles

The nonadjacent angles formed by two intersecting lines