Transcript Did you ever wonder why…

Congruent
Triangles
1
2
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.
3
Congruent Triangles - CPCTC
CPCTC: Corresponding Parts of Congruent Triangles are Congruent
Two triangles are congruent IFF their corresponding parts
(angles and sides) are congruent.
A
If
ABC PQR
A ↔ P; B ↔ Q; C ↔ R
B
C
≡
Vertices of the 2 triangles correspond in the same order
as the triangles are named.
P
Corresponding sides and angles of the two congruent triangles:
AB  PQ
B  Q
BC  QR
C  R
AC  PR
Q
≡
A  P
R
Congruent Triangles
B
C


Z
____

Y
_____

X
______
B
=
A 
ZY
A
X
=
ZX
AC  ____
Z
≡ ≡
AB  ____
ZY
YX
BC  ____
C
Note:
∆ABC

∆
ZYX
______
∆ABC

∆XYZ
Lesson 4-2: Congruent Triangles
4
Y
5
Example…………
When referring to congruent triangles (or polygons), we must
name corresponding vertices in the same order.
R
Y
A
N
U
S
R
U
A
N
Y
SUN  RAY
Also NUS  YAR
Also USN  ARY
S
6
Example ………
If these polygons are congruent, how do you name them ?
P
O
U
N
M
E
A
T
S
R
1. Pentagon MONTA  Pentagon PERSU
2. Pentagon ATNOM  Pentagon USREP
3. Etc.