Geometry Properties Review

Definition of a Congruent

Segments or angles that have the same measure (Used when you switch from an "=" sign to a "≅" sign or vice versa)

Definition of a Bisector

a line or segment that intersects a segment or angle and divides it into two congruent halves

Definition of a Midpoint

divides the segment into two congruent segments

Definition of Complementary Angles

two angles whose degree measures have a sum of 90º

Definition of Supplementary Angles

two angles whose degree measures have a sum of 180º

Vertical Angles

are always congruent and you can assume from a picture

Linear Pair

you can assume from a picture; they are supplementary

Reflexive Property

A line segment (or angle) is congruent to itself

Symmetric Property

a=b, b=a; 8=x, x=8

Transitive Property

a=b, b=c, a=c [usually not = to a #]

Addition Property

The same thing can be added to both sides of an equation

Subtraction Property

The same thing can be subtracted from both sides of an equation

Multiplication Property

You can multiply both sides of an equation by the same thing

Division Property

You can multiply both sides of an equation by the same thing (except 0)

Substitution Property

Replace a variable or value with an equal variable or value

Distributive Property

a(b+c)=ab+ac

Definition of Perpendicular Lines

Two intersecting lines that form four right angles

Definition of a Right Angle

measures 90º

Triangle Sum Theorem

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

Definition of Isosceles Triangle

a triangle that has two congruent sides

Exterior angle of a Triangle

The exterior angle of a triangle is equal to the sum of the two opposite interior angles.