Point
an undefined term that has has no dimension.
Line
an undefined term; it extends in one dimension.
Plane
an undefined term; it extends in two dimensions.
Collinear points
Points that lie on the same line
Coplanar points
Points that lie on the same plane
line segment
part of a line with two endpoints
ray
a part of a line that begins at a point and continues without end in one direction
initial point
the endpoint of a ray
opposite rays
two rays are opposite to each other iff they have the same endpoint and they are collinear
postulate
a rule that is accepted without proof
ruler postulate
The points on a line can be matched one to one with real numbers. The real number that corresponds to a point is the coordinate of the point. The distance between points A and B, written as AB, is the absolute value of the difference between the coordinat
segment addition postulate
If B is between A and C, then AB+BC=AC
distance formula
d = ?[( x? - x?)� + (y? - y?)�]
congruent segments
Segments that have the same length
angle
consists of two different rays that have the same initial point
vertex
The common endpoint of an angle
angle addition postulate
If P is in the interior of <RST, then m<RSP + m<PST = m<RST
acute angle
an angle less than 90 degrees but more than 0 degrees
right angle
an angle that measures 90 degrees
obtuse angle
An angle that measures more than 90 degrees but less than 180 degrees
straight angle
an angle that measures 180 degrees
reflex angle
an angle that is more than 180 degrees but less than 360 degrees
adjacent angles
are a pair of angles with a common vertex and a common side, but no common interior points
midpoint
a point that divides a segment into two congruent segments
bisects
divides into two congruent parts
segment bisector
a segment, ray, line, or plane that intersects a segment at its midpoint
midpoint formula
[(x1+x2)/2, (y1+y2)/2] or the average of the x-coordinates and the average of y-coordinates of a line segment
angle bisector
a ray that divides an angle into two congruent angles
vertical angles
two angles whose sides form two pairs of opposite rays
linear pair
two adjacent angles whose noncommon sides are opposite rays
complementary angles
two angles whose measures have a sum of 90 degrees
supplementary angles
two angles whose measures have a sum of 180 degrees