Summary Geometry proofs easy cheat sheet

GEOMETRY PROOFS ONE-PAGE CHEAT
SHEET

1. Most Common Reasons Used in Proofs
These show up in almost every single proof:

Angles & Lines
● Vertical angles are congruent

● Linear pair → supplementary

● Supplementary angles sum to 180°

● Complementary angles sum to 90°

● Perpendicular lines → right angles

● Right angles are congruent

● Parallel lines →

○ Corresponding angles are congruent

○ Alternate interior angles are congruent

○ Same-side interior angles are supplementary


Segments
● Midpoint definition: divides a segment into 2 congruent parts

● Segment bisector: creates 2 congruent segments

● Reflexive property: a segment or angle is congruent to itself


Triangles
● SSS: 3 matching sides → triangles congruent