Acute Angle
An angle that measures greater than 0� and less than 90�
Adjacent Angles
Two angles in the same plane with a common vertex & a common side, but no common interior points (right next to)
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 nonoverlapping unit squares of a given size that will exactly cover the interior of a plane figure
Base
When finding the area of a triangle this can be any side of a triangle
Between
Given three points A, B, and C, B is between A and C iff all three points lie on the same line, and AB + BC = AC
Bisect
To divide into two congruent parts (cut in half)
Circle
A round plane figure whose boundary consists of points equidistant from a fixed point called the center.
Circumference
The distance around the circle
Collinear
Points that lie on the same line
Complementary Angles
Two angles whose measures have a sum of 90�
Congruent Angles
Angles that have the same measure
Congruent Segments
Two segments that have the same length
Construction
A method of creating a figure that is considered to be mathematically precise
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 & a vertical line called the y-axis
Coplanar
Points that lie in the same plane
Degree
A unit of angle measure
Diameter
A segment that passes through the center of a circle & whose endpoints are on the circle
Distance
The absolute value of the difference of the coordinates of two points
Endpoint
A point at an end of a segment or the starting point of a ray
Exterior of an Angle
The set of all points outside an angle
Height
When finding the area of a triangle this segment, from a vertex, 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
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 straight path that has no thickness and extends forever
Linear Pair
A pair of adjacent angles whose noncommon sides are opposite rays
Measure
The use of units to find a size or quantity
Midpoint
The point that divides a segment into two congruent segments
Obtuse Angle
An angle that measures greater than 90� and less than 180�
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
Perpendicular Bisector
A line, segment, or ray that divides a line segment into two equal parts & creates a right angle with the line segment
Pi
The ratio of the circumference of a circle to its diameter, denoted by the Greek letter ?
Plane
A flat surface that has no thickness and extends forever
Point
A location that has no size
Position
The location of a shape in the coordinate plane
Postulate
A statement that is accepted as true without proof, also called an axiom
Preimage
The original figure in a transformation
Radius
A segment whose endpoints are the center of a circle and a 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
Right Angle
An angle that measures 90�
Rotation
A transformation about a point P, 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 formed by two opposite rays that measures 180�
Supplementary Angles
Two angles whose measures have a sum of 180�
Transformation
A change in the position, size, or shape of a figure
Translation
A transformation in which all the points of a figure move 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 an angle
Vertical Angles
The nonadjacent angles formed by two intersecting lines
X-Value
The horizontal value in a pair of coordinates
Y-Value
The vertical value in a pair of coordinates