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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