Undefined Terms
The 3 most basic figures in geometry which cannot be defined using other figures: point, line, and plane
Point
Names a location and has no size. It is represented by a dot.
Line
Straight path that has no thickness and extends forever.
Plane
Flat surface that has no thickness and extends forever
Line segment
Part of a line consisting of two points and all points between them
Endpoint
Point at one end of a line segment or the starting point of a ray
Ray
Part of a line that starts at an endpoint and extends forever in one direction.
Opposite rays
Two rays that have a common endpoint and form a line.
Collinear points
Points that lie on the same line
Coplanar points
Points that lie in the same plane
Postulate
A statement that is accepted as true without proof
Congruent segments
Segments that have the same length
Midpoint
The point on a line segment that bisects, or divides, the segment into two congruent segments.
Angle
Figure formed by two rays, or sides, with a common endpoint.
Vertex
The common endpoint of an angle. (A point where two lines meet)
Measure of an angle
Given in degrees using protractor with a range from 0 degrees to 180 degrees.
Acute Angle
An angle that measures greater than 0 degrees and less than 90 degrees
Right Angle
An angle that measures 90 degrees
Obtuse Angle
An angle that measures greater than 90 degrees and less than 180 degrees
Straight Angle
An angle formed by two opposite rays and measures 180 degrees
Congruent Angles
Angles that have the same degree measure
Angle Bisector
A ray that divides an angle into two congruent angles
Complementary Angles
Two angles whose measures add up to 90 degrees
Supplementary Angles
Two angles whose measures add up to 180 degrees
Adjacent Angles
Two angles in the same plane with a common vertex and a common side but no common interior points
Linear Pair Angles
A pair of adjacent angles whose noncommon sides are opposite rays forming a line
Vertical Angles
Two nonadjacent angles formed by two intersecting lines
Parallel Lines
Coplanar lines that do not intersect
Perpendicular Lines
Coplanar lines that form right angles-90 degree angles.
Degree
A measure of an angle based upon 360 degrees in a circle. 1 degree = 1/360 of a circle