Cechy przystawania trójkątów - rules of congruency for triangles:
- SSS - side-side-side
- SAS - side-angle-side (included angle)
- ASA - angle-side-angle (included side)
- AAS - angle-angle-side (non included side)
Cechy podobieństwa trójkątów - rules of similarity for triangles:
- (AAA) - angle-angle-angle
- (AA) - angle-angle
- (SSS~) - sides proportional
- (SAS~) - eaqual included angle, sides proportional
cechy podzielności - tests for divisibility