Congruent

1
Lesson 4-2

• Congruent
• Triangles

2
Congruent Figures
Common English
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.
Precise Math / Logic
3
Does this pair appear to be congruent?
Does this pair appear to be congruent?
Does this pair appear to be congruent?
4
Congruent Triangles
Two triangles are congruent IFF their vertices
can be matched up so that the corresponding parts
(angles and sides) of the triangle are congruent.
5
Congruent Triangles
Two triangles are congruent IFF their vertices
can be matched up so that the corresponding parts
(angles and sides) of the triangle are congruent.
1. ?A ? ?R 2. ?B ? ?S 3. ?C ? ?T 4. AB ? RS
5. BC ? ST 6. CA ? TR
?ABC ? ?RST
A
R
iff
C
B
T
S
6
Congruent Triangles
Two triangles are congruent IFF their vertices
can be matched up so that the corresponding parts
(angles and sides) of the triangle are congruent.
1. ?A ? ?R 2. ?B ? ?S 3. ?C ? ?T 4. AB ? RS
5. BC ? ST 6. CA ? TR
?ABC ? ?RST
A
S
T
iff
C
B
R
7
Watch Carefully !!!!!
A
A
Because
C
B
B
C
?ABC ? ?ABC
8
But . . .
A
A
Because
C
B
B
C
?ABC ? ?ACB
9
When referring to congruent triangles (or
polygons), we must name corresponding vertices in
the same order.
R
S U N
R A Y
Y
A
U
N
?SUN ? ?RAY
Also ?NUS ? ?YAR
S
Also ?USN ? ?ARY
10
How would you write that these two figures are
congruent?
Write your answer on a piece of paper.
P
O
U
M
N
E
T
A
S

• Pentagon MONTA ? Pentagon PERSU
• Pentagon ATNOM ? Pentagon USREP
• Etc.

R