Geometry

space

set of all points; has length, width, and depth

collinear points

points are collinear iff they are on the same line

coplanar points

points are coplanar iff they are on the same plane

non-collinear points

points are not collinear iff they are not on the same line

non-coplanar points

points are not coplanar iff they are not on the same plane

postulate

a rule we accept as true without proof

betweenness of points

B is between A & C iff they are collinear and AB + BC = AC

congruent segments

segs are congruent iff their lengths are equal

midpoint of a segment

a point is a midpoint of a segment iff it divides the segment into 2 congruent segs/2 equal lengths

bisector

the line, point, plane, or segment that goes through the midpoint of a seg

opposite rays

when rays are opposite rays, it is implied that the endpoint is between the other points

angles

rays with the same vertex

acute angle

an angle is acute iff its measure is less than 90 degrees

right angle

an angle is a right angle iff the measurement is 90 degrees

congruent angle

angles are congruent iff their measurements are equal

obtuse angles

an angle is an obtuse angle iff its measurement is more than 90 degrees and less than 180 degrees

straight angle

an angle is a straight angle iff its measurement is equal to 180 degrees

betweenness of rays

Ray OB is between rays OA and OC iff they are coplanar and m

bisector of an angle

a ray is a midray of an angle iff it divides the angle into 2 congruent angles/2 equal measures