Geometry Vocab unit 1

Unit 1

(keep going to learn vocab words from Unit 1)

point

a location in space with no definite size or dimension

line

a straight path that extends infinitely in both directions with no thickness or endpoints

collinear points

points that lie on the same straight line

segment

part of a line with two endpoints

ray

part of a line with one endpoint and extending infinitely in one direction

vertical angles

two nonadjacent angles formed by intersecting lines that are congruent

linear pair

two adjacent angles whose noncommon sides form a straight line

parallel lines

lines in the same plane that never intersect

perpendicular lines

lines that intersect to form right angles

skew lines

noncoplanar lines that do not intersect and are not parallel

plane (face)

a flat surface that extends infinitely in all directions

coplanar

points or lines that lie on the same plane

angle

a figure formed by two rays with the same endpoint

vertex

the common endpoint of the sides of an angle

legs

the sides that form an angle or triangle other than the base

interior of angle

the region inside the rays of an angle

exterior of angle

the region outside the rays of an angle

acute angle

an angle that measures greater than 0° and less than 90°

obtuse angle

an angle that measures greater than 90° and less than 180°

right angle

an angle that measures exactly 90°

straight angle

an angle that measures exactly 180°

reflex angle

an angle that measures greater than 180° and less than 360°

supplementary

two angles whose measures add up to 180°

transversal

a line that intersects two or more other lines in a plane at different points

corresponding angles

angles in matching positions when a transversal crosses two lines

alternate interior angles

nonadjacent interior angles on opposite sides of a transversal

consecutive interior angles

interior angles on the same side of a transversal

corresponding angles theorem

if a transversal intersects parallel lines, then corresponding angles are congruent

consecutive interior angles theorem

if a transversal intersects parallel lines, then consecutive interior angles are supplementary

alternate interior angles theorem

if a transversal intersects parallel lines, then alternate interior angles are congruent

converse of the corresponding angles theorem

if two lines are cut by a transversal so that corresponding angles are congruent, then the lines are parallel

converse of the alternate interior angle theorem

if two lines are cut by a transversal so that alternate interior angles are congruent, then the lines are parallel

converse of the consecutive interior angles theorem

if two lines are cut by a transversal so that consecutive interior angles are supplementary, then the lines are parallel

reflexive property

any quantity is equal to itself

symmetric property

if a = b then b = a

transitive property

if a = b and b = c then a = c

distributive property

a(b + c) = ab + ac

substitution property

if a = b then b can replace a in any expression

addition property

if a = b then a + c = b + c

subtraction property

if a = b then a − c = b − c

multiplication property

if a = b then ac = bc

division property

if a = b, then a ÷ c = b ÷ c

partition property

a whole is equal to the sum of its parts

adjacent angles

two angles that share a common vertex and a common side but have no overlap

complementary angles

two angles whose measures add up to 90°

congruent supplements theorem

angles supplementary to the same angle or congruent angles are congruent

congruent complements theorem

angles complementary to the same angle or congruent angles are congruent

lines perpendicular to a transversal theorem

if a transversal is perpendicular to one of two parallel lines, then it is perpendicular to the other as well

perpendicular transversal theorem

if a line is perpendicular to one of two parallel lines, then it is perpendicular to the other line too