**Geometry Chapter 4.2 Congruence and Triangles**

**I) Vocabulary**:

A) When two figures are congruent, there is a correspondence between their angles and sides such that corresponding angles are congruent and corresponding sides are congruent.

**Example:**Given Δ ABC is congruent to Δ PQR then we know

1) angle A = angle P, angle B = angle Q, and angle C = angle R

2) AB = PQ, BC = QR, and AC = PR

Make sure that you list the corresponding angles in the same order with the triangle congruence.

**Example**: ΔABC = ΔDEF is not the same as ΔABC = ΔEFD.

**B) Third Angles Theorem**- if two angles of one triangle are congruent to two angles of another triangle, then the third angles are also congruent.

**C) Reflexive Postulate**- Every triangle is congruent to itself

**D) Symmetric Postulate**- If ΔABC = ΔDEF, then ΔDEF = ΔABC

**E) Transitive Postulate**- If ΔABC = ΔDEF and ΔDEF = ΔJKL, then ΔABC = ΔJKL