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Acute Angle

an angle less than 90 degrees but more than 0 degrees

Alternate Exterior Angles

Angles that lie outside a pair of lines and on opposite sides of a transversal.

Alternate Exterior Angles Converse

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

Alternate Interior Angles Converse

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

Alternate Interior Angles Theorem

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


A point and 2 line segments

Angle Addition Postulate

if point B lies in the interior of <AOC then m<AOB+m<BOC=m<AOC

Angle Bisection

Occurs when a ray bisects an angle

Angle of rotation

angle formed by rays drawn from the center of rotation to a point and its image


the number of square units needed to cover a flat surface

Base Angles Theorem

if two sides of a triangle are congruent, then the angles opposite them are congruent


The space between two points


To cut into 2 equal pieces

Collinear (points)

points that lie on the same line


drafting instrument used for drawing circles

Complementary Angles

two angles whose sum is a right angle/90 degrees


Having the same measure

Congruent Complements Theorem

if two angles are complementary to the same angle (or to congruent angles) then the two angles are congruent

Congruent Supplements Theorem

if two angles are supplementary to the same angle (or to congruent angles) then they are congruent


reasoning that involves the formation of conclusions from incomplete evidence


drawing a figure satisfying certain conditions as part of solving a problem or proving a theorem

Legs of a right triangle

the sides that make up the 90 degree angle of a right triangle

Consecutive Interior Angles

angles that are on the same side of the transversal and inside the two lines

Consecutive Interior Angles Converse

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


a number that identifies a position relative to an axis


lying in the same plane


an example that shows a conjecture is false


clarity of outline

Direction of a vector

Determined by the angle that the vector makes with a horizontal line.


the property created by the space between two objects or points

Distance Formula

d = √[( x₂ - x₁) + (y₂ - y₁)]


points on the ends of line segments


all angles are congruent


the side of a right triangle opposite the right angle

Inductive Reasoning

reasoning from detailed facts to general principles


a copy of a Preimage by a translation, rotation, ect...

Initial Point of a Ray

The endpoint on a ray


-3, -2, -1, 0, 1, 2, 3


A point where two or more Lines, line segments, ect cross each other

Isosceles Triangle

A triangle with two congruent sides

Legs of an Angle

are the two congruent sides in a isosceles triangle

Legs of a Right Triangle

in a right triangle the sides that form the right angle are called legs of the right triangle. the side opposite the right angle is the hypotenuse of the triangle


the linear extent in space from one end to the other

Linear Angle

Angle that is exactly 180 degrees

Linear Pair

Two adjacent angles that form a straight line

Linear Pair Postulate

If two angles form a linear pair, then they are supplementary


A line with no endpoint

Line Segment

part of a line with two endpoints

Magnitude of a vector

AB is the distance from the initial point A to the terminal point B, and is written |AB|

Measure of an Angle

number of degrees in an angle


a point that divides a segment into two congruent segments

Midpoint Formula

(x₁+x₂)/2, (y₁+y₂)/2

Natural Numbers

each positive whole number


measuring stick consisting of a strip of wood or metal or plastic with a straight edge that is used for drawing straight lines and measuring lengths

Opposite Rays

2 rays that have the same endpoint and go in opposite directions forming a line

Perpendicular Transversal

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


(mathematics) an unbounded two-dimensional shape


Specific coordinate on a line, line segment, plane, ect...


rules that are accepted without proof


The original figure in a transformation.


drafting instrument used to draw or measure angles


(mathematics) a straight line extending from a point


fixed and unmoving

Segment Bisector

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

Sides of an Angle

the rays that form the angle


hand tool consisting of a flat rigid rectangular bar (metal or wood) that can be used to draw straight lines (or test their straightness)

Undefined Term

A basic figure that is not defined in terms of other figures. The undefined terms in Geometry are point, line, and plane.


the point of intersection of lines or the point opposite the base of a figure

Right Angle

the 90 degree angle between two perpendicular lines

Obtuse Angle

an angle between 90 and 180 degrees


The distance around a figure

Straight Angle

An angle that is exactly 180 degrees

Real Numbers

Every number


The translation of a figure in which the object flips

Reflex Angle

an angle greater than 180 degrees (but less than 360)

Remote Interior Angles Theorem

the exterior angles of a triangle euquals the sum of the 2 remote interior angles.

Right Triangle

a triangle with one right angle

Right Angle Congruence Theorem

all right angles are congruent


(mathematics) a transformation in which the coordinate axes are rotated by a fixed angle about the origin

Scalene Triangle

a triangle with no two sides of equal length

Sides of an Angle

the rays that form the angle

Supplementary Angles

Two angles whose sum is 180 degrees


(mathematics) a transformation in which the origin of the coordinate system is moved to another position but the direction of each axis remains the same

Triangle Sum Theorem

The sum of the measures of the angles of a triangle is 180.


a straight line segment whose length is magnitude and whose orientation in space is direction

Verticle Angle

formed by 2 intersecting like and are opposites of each other which means angles are congruent

Verticle Angle Theorem

verticle angles are congruent

Whole Numbers

0 and the natural numbers

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