Geometry Proofs and Theorems

Flashcards covering formal proofs, triangle properties, and geometric postulates and theorems.

Similar Triangles

Sides are in proportion. Use AA, SAS, SSS.

Congruent Triangles

Sides and angles are congruent. Use SSS, ASA, AAS, SAS, HL.

Reflexive Postulate

A segment or angle is congruent to itself.

Definition of Midpoint/Bisector

If C is the midpoint of AB, then AC ≅ CB.

Sum of angles in a triangle

Angles in a triangle add up to 180°.

Alternate Interior Angles

Form a Z shape.

Consecutive Angles

Form a C shape.

Linear Pair

Angles on a line add up to 180°.

Transitive Property

If A = B and B = C, then A = C.

Addition Postulate

If A = B and C = D, then A + C = B + D.

Subtraction Postulate

If A = B and C = D, then A − C = B − D.

All right angles are…

Congruent

Vertical Angles

Form an X shape.

Linear Pair Angles

Angles that form a linear pair are supplementary (add to 180°).

Supplements of angles

Are congruent

Complements of angles

Are congruent

Halves of lines/angles

Are congruent

Acute angles of right triangles

Are complementary.

Triangle Inequality Theorem

The sum of 2 sides of a triangle is greater than the 3rd side.

CPCTC

Corresponding Parts of Congruent Triangles are Congruent