##### chapter 1

9th grade, 10th grade

undefined term

ex; point, line, plane

point

a location, has neither size or shape

line

made up of points and has no thickness or width

plane

a flat surface made up of points that extends indefinitely in all directions

collinear

points that lie on the same line

coplanar

points that lie on the same plane

intersection

The set of points they have in common, two lines intersect at one point

definition

explained using undefined terms and/or other defined terms

defined term

explained using undefined terms and/or other defined terms

space

defined as boundless

line segment

a straight line which links two points without extending beyond them

betweenness of points

a point is between two other points on the same line

between

in a space separating two objects

congruent segments

segments that have the same measure

construction

methods of creating geometric figures without the benefit of measuring tools

distance

the length of the segment with those points as its endpoints

midpoint

the point halfway between the endpoints of the segment

segment bisector

any segment, line or plane that intersects a segment at its midpoint

ray

a part of a line

opposite rays

two rays with a common endpoint that point in opposite directions and form a straight line.

angle

formed by two noncollinear rays that have a common endpoint

side

the rays

vertex

the common endpoint

interior

the space inside of an angle

exterior

the space outside of an angle

degree

a measurement of plane angle; 1/360

right angle

an angle whose measure is exactly 90°

acute angle

an angle whose measure is less than 90°

obtuse angle

an angle whose measure is greater than 90° and less than 180°

angle bisector

a ray that divides an angle into two congruent angles

adjacent angles

two angles that lie in the same plane and have a common vertex and a common side, but no common interior points

linear pair

a pair of adjacent angles with no common sides that are opposite rays

vertical angles

two adjacent angles formed by two intersecting lines

complementary angles

two angles with measures that have a sum of 90

supplementary angles

two angles with measures that have a sum of 180

perpendicular

lines, segments, rays that form right angles