Angle

A point

Vertex

Line

An infinite set of points that extends forever in both directions infinitely

Line Segment

A section of a line connecting two endpoints with a specific length

Ray

Intersecting Lines

Adjacent Angles

Two angles that share a common side and vertex

Angle Bisector

A line or segment that divides an angle into 2 congruent angles

Perpendicular Lines

(always 2 steps in a proof)

Right Angle

Acute Angles

Angles less than 90 degrees

Obtuse Angles

Angles more than 90 degrees but less than 180 degrees

Straight Angle

An angle whose measure = 180 degrees

Complementary Angles

Angles that add up to = 90 degrees

Supplementary Angles

Angles that add up to = 180 degrees

Angles around a point

Add up to = 360 degrees

Linear Pair

2 Angles that form a line and add up to = 180 degrees

Vertical Angles

are congruent

Parallel Lines

Alternate Interior Angles

with 2 parallel lines cut by a transversal, alternate interior angles are congruent

Alternate Exterior Angles

with 2 parallel lines cut by a transversal, alternate exterior angles are congruent

Same Side Interior Angles

with 2 parallel lines cut by a transversal, same side interior angles are supplementary (add up to = 180 degrees)

Same Side Exterior Angles

with 2 parallel lines cut by a transversal, same side exterior angles are supplementary (add up to = 180 degrees)

Corresponding Angles

with 2 parallel lines cut by a transversal, corresponding angles are congruent

Lines are parallel when...

alternate interior angles are congruent OR

alternate exterior angles are congruent OR

corresponding angles are congruent OR

same side interior angles are supplementary OR

same side exterior angles are supplementary