### Section 4.4 ~ Using CPCTC!

```BELL WORK
1) List the five ways to prove two triangles
congruent.
2) Complete each sentence below:
 Class starts when the _______________.
• We do not _____________when the
teacher is talking.
___________________are to be treated
with respect.
LETS USE CPCTC!
Objective: Be able to use CPCTC to find unknowns in
congruent triangles!
Are these triangles congruent? By which postulate/theorem?
L
J
ΔLJK
MNK
_____
N
K
@ _____
M
Oh, and what is the Reflexive Property again?
It says something is equal to itself. EX
ÐA @ ÐA
AB @ AB
We learn by doing,
and in the process
you're going to
few times...
though I didn't
think you'd take it
quite that
literally.
C.P.C.T.C.
Once you have shown triangles are congruent, then you
can make some CONCLUSIONS about all of the
sides and __________)
angles
corresponding parts (_______
of
those triangles!
Corresponding Parts of
Congruent Triangles are
CONGRUENT!!
Are the triangles congruent? By which postulate or
theorem?
B
Y
Z
C
A
What other parts of
the triangles are
congruent by CPCTC?
ÐB @ ÐY
AB @ ZY
BC @ YX
X
Yes; ASA
If <B= 3x and ,Y = 5x –9,
find x.
9
x
2
3x = 5x - 9
9 = 2x
Given:
1   2
C
3 4
L
SL  SR
Prove:
3   4
1
S
2
Given
CS  CS
2. _______________
2. Reflexive
SAS
3  4
4. _______________
CPCTC
4. ___________
R
Given:
Prove:
RC  HV
AR  EH
CA  VE
C
R  H
A
V
R
H
E
RC  HV ; AR  EH; CA  VE 1. Given
1. _____________________
CRA  VHE
2. _____________________
2. SSS
R  H
CPCTC
3. _____________________
3. ________
State why the two triangles are congruent and write
the congruence statement. Also list the other pairs
of parts that are congruent by CPCTC.
R
C
ÐY @ ÐQ
Y Q
P
T
AAS
CT @ RP
CY @ RP
A geometry class is trying to find the distance across a small
lake. The distances they measured are shown in the diagram.
Explain how to use their measurements to find the distance
across the lake.
30 yd
40 yd
40 yd
24.5 yd
30 yd
Vertical angles are congruent.
The triangles are congruent by SAS.
The width of the lake has to be 24.5 yd by CPCTC.
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