1. Lesson 4-2: Congruent Triangles

2. Lesson 4-2: Congruent Triangles
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

3. Congruent Triangles - CPCTC
Corresponding Parts of Congruent Triangles are Congruent
Two triangles are congruent IFF their corresponding parts (angles and sides) are congruent. B C A Q R P = │
Vertices of the 2 triangles correspond in the same order as the triangles are named. ≡
A ↔ P; B ↔ Q; C ↔ R
Corresponding sides and angles of the two congruent triangles: │ = ≡
Lesson 4-2: Congruent Triangles

4. Lesson 4-2: Congruent Triangles
CPCTC
≡ DEF
ABC
WHICH ANGLES ARE CONGRUENT?
Lesson 4-2: Congruent Triangles

5. Lesson 4-2: Congruent Triangles
 Z B A C X Y Z =
 Y
 B  _____ ≡ │ ≡
 X │
 C  ______ =
Note:
∆ ZYX
∆ABC  ______
∆ABC  ∆XYZ
Lesson 4-2: Congruent Triangles

6. Lesson 4-2: Congruent Triangles
THIRD ANGLES THEOREM
Lesson 4-2: Congruent Triangles

7. Lesson 4-2: Congruent Triangles
Example…………
When referring to congruent triangles (or polygons), we must name corresponding vertices in the same order. S U N R A Y R Y
SUN  RAY A N U
Also NUS  YAR
Also USN  ARY S
Lesson 4-2: Congruent Triangles

8. Lesson 4-2: Congruent Triangles
Example ………
If these polygons are congruent, how do you name them ? P O U N M E A T S R
Pentagon MONTA  Pentagon PERSU
Pentagon ATNOM  Pentagon USREP
Etc.
Lesson 4-2: Congruent Triangles

9. Lesson 4-2: Congruent Triangles
REFLEXIVE PROPERTY A
AD is congruent to AD by the reflexive property. B C D
Lesson 4-2: Congruent Triangles