Transcript 4.1 Congruent Figures

Geometry
4.1 Congruent Figures
Congruent Figures
• Two objects are congruent (
the same size and shape

) if they have
• Two figures are congruent if and only if their
vertices can be matched up so that
corresponding parts (angles and sides) of the
figures are congruent.
• When writing which figures are congruent, be
sure to write the vertices in the same order.
A
R
B
C
Triangle ABC
S
T
Triangle RST
A
R
B
C
Triangle ABC

S
T
Triangle RST
D
A
B
M
J
C
Quadrilateral ABCD
K
L
Quadrilateral JKLM
D
A
B
M
J
C
Quadrilateral ABCD
K

L
Quadrilateral JKLM
Congruent Figures
• Sometimes you have to change the position of
the figures to match up vertices
• Practice “spinning” and “sliding” the figures
mentally
SPIN and SLIDE
Defn. of Congruent Triangles

• Two triangles are congruent (
) if and
only if their vertices can be matched up so that
the corresponding parts (angles and sides) of
the triangles are congruent.
A
E
D
B
C
F
Defn. of Congruent Triangles

• Two triangles are congruent (
) if and only
if their vertices can be matched up so that the
corresponding parts (angles and sides) of the
triangles are congruent.
∆ ABC  ∆ DEF
7
C
AB
BC
B
C
E
F
CA
D
E
7
7
B






7
D
7
A
A
7
The order must match.
F
DE
EF
FD
CPCTC
• When the definition of congruent
triangles is used in a proof, use the
wording:
“corresponding parts of congruent triangles are congruent”
CPCTC
Name 3 pairs of corresponding sides.
M
Name 3 pairs of corresponding angles.
Is it correct to say MAN  BOY ?
A
B
O
N
Y
Complete the statements given ABO  CDO .
.
DOC  __________
BAO  __________
AB  __________
CO  __________
AOB  __________
D
C
O
Why is AB DC ?
A
B
B
I
G
T
Name the coordinates of B, I, and G.
Name the coordinates of a point D, such that
.
BIG  DIG
Name the coordinates of a point O, such that . BIG  TOP
P
Homework
• pg. 120 #1-6, 10-13, (15-21 odd)
• Makeups next week are Wednesday after school
• Graphing Calculator?