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
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
