1. Section 4-3 Congruent Triangles

2. Vocabulary
Congruent Triangles -Triangles that are the same size and shape.
Each triangle has three sides and three angles.
If all sides and angles of the corresponding parts of two triangles are congruent, then the triangles are congruent.

3. The Right Match
Congruent Not congruent A D F E C B

4. Corresponding sides and anglesT A B S R
Corresponding Angles
Corresponding sides
AB RS
BC ST
Congruence Statement:
AC RT

5. H B A C K J

6. Definition of Congruent Triangles (CPCTC)
Two triangles are congruent if and only if their corresponding parts are congruent.
CPCTC- Corresponding Parts of Congruent Triangles are Congruent

7. In the diagram, ΔITP  ΔNGO. Find the values of x and y.
O  P CPCTC
mO = mP Definition of congruence
6y – 14 = 40 Substitution
6y = 54 Add 14 to each side.
y = 9 Divide each side by 6.
CPCTC
NG = IT Definition of congruence
x – 2y = 7.5 Substitution y = 9
x – 18 = 7.5 x = 25.5, y = 9

8. Complete the two-column proof.
Prove: ΔLMN  ΔPON
Statements Reasons 1.
1. Given
2. LNM  PNO
2. Vertical Angles Theorem
3. M  O
3. Third Angles Theorem
4. ΔLMN  ΔPON
4. CPCTC

9. Find the missing information in the following proof.
Prove: ΔQNP  ΔOPN
Reasons
Statements 1.
1. Given 2.
2. Reflexive Property of Congruence
3. Q  O, NPQ  PNO
3. Given 4.
Third angle theorem
4. QNP  ONP
5. ΔQNP  ΔOPN
5. Definition of Congruent Polygons

10. Assignment #38
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