Lesson 4-2

Congruent Triangles

Lesson 4-2: Congruent Triangles 1

Congruent Figures

Congruent figures are two figures that have the same size and shape.

IF two figures are congruent THEN they have the same size and shape.

IF two figures have the same size and shape THEN they are congruent.

Two figures have the same size and shape IFF they are congruent.

Lesson 4-2: Congruent Triangles 2

Congruent Triangles - CPCTC

CPCTC:

Corresponding Parts of Congruent Triangles are Congruent

If

Two triangles are congruent IFF their corresponding parts (

angles and sides

) are congruent.

ABC



PQR

A Vertices of the 2 triangles correspond in the same order as the triangles are named.

A ↔ P; B ↔ Q; C ↔ R

B Corresponding sides and angles of the two congruent triangles:

P Q



C

 

R A B



PQ BC



Q R A C



P R

Q Lesson 4-2: Congruent Triangles P 3 C R



A

 

B

 

C



AB



Congruent Triangles

B C

ZY

≡ ≡ Z

BC



AC

 A

Note:

∆ABC 

∆ABC

 X

∆XYZ

Y Lesson 4-2: Congruent Triangles 4

Example…………

Y N

When referring to congruent triangles (or polygons), we must name corresponding vertices in the same order.

R U A S U N R A Y



SUN

 

RAY Also



NUS

 

YAR Also



USN

 

ARY S

Lesson 4-2: Congruent Triangles 5

Example ………

If these polygons are congruent, how do you name them ?

P O U M N E A T S R 1. Pentagon MONTA



Pentagon PERSU 2. Pentagon ATNOM



Pentagon USREP 3. Etc.

Lesson 4-2: Congruent Triangles 6