Download 4.3 Using Congruent Triangles

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State if the two triangles are congruent. If yes, state
how you know (postulate).
1.
2.
4.
3.
5.
Geometry
4.3 Using Congruent Triangles
LEQ: How do you deduce information about
segments or angles once we prove that two
triangles are congruent?
Earlier you learned how to prove two
triangles congruent by
SSS
SAS
ASA
After we prove  Δ’s …….today we
will prove  segments or angles
using CPCTC
If 2 triangles are
congruent
All of their 6
corresponding parts are
congruent
A Way to Prove Two Segments or
Two Angles Congruent
1. Identify 2 triangles in which the 2
segments or angles are corresponding
parts
2. Prove that the 2 triangles are congruent
(use SSS, ASA, or SAS)
3. State that the 2 parts are congruent,
using the reason CPCTC
Plan the Proof:

Prove: Q

7
Plan:
1

Δ PQR

1
2
S


R
S
2
PS
PR
Δ PSR by SAS, so
7
7
PR
P
Q

7
7
PQ
QPS
PS
7
PQ
7
Given: PR bisects
Q
S (CPCTC)
Plan the Proof:
ZW

Prove: WX
WX
ZW
ZX
Δ ZWX

so WX
Y
3
XY
ZY
W
 YZ


ZX

ZY because Alt Int. <‘s 
1
4
X
XY
Δ XYZ by SSS, so
2
1
7
Plan:
Z
 YZ
7
Given: WX
2 (CPCTC),
lines
Lines
to a Plane
A
Given:
M is the midpoint of AB
plane X
AB at M
X
M
What can you conclude about AP and BP ?
Plan:
Δ APM
so AP


Δ BPM by SAS
BP (CPCTC)
B
P
Let’s try a few from the HW
Open your books to page 130
#2 and #4
Homework
pg. 130 # 1 - 8
Bell Ringer
Agenda



I will put you into groups to work on a
worksheet
Tomorrow: Review for Quiz (packet)
Thursday: Quiz on 4.1-4.3
Worksheet

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