1. ABC DEF? Is Do Now: When two triangles are congruent:
Introduce car part story
When two triangles are congruent:

2. Name the 6 pairs of corresponding parts:

3. GOOD NEWS!!
To prove triangles are
we only need to show 3 pairs of corresponding parts of the triangles are

4. Not-so-Good News!!
Proofs are TRICKY about WHICH 3 sets of corresponding parts are congruent.

5. How do we prove triangles are congruent?
AIM:
How do we prove triangles are congruent?

6. 3 sides of one
3 sides of another

7. 2 sides and the included angle of one are
to the corresponding parts of another

8. 2 angles and the included side of one are
to the corresponding parts of another

9. 2 angles and the non-included side of one are
to the corresponding parts of another
22º
22º

11. NOT
ASS

12. Ex 1
Which of the following cannot be used to prove triangles are congruent?
a. SSS
SSS
b. AAA AAA
c. SAS SAS
d. AAS AAS

13. Identify congruent triangles. Why are they congruent?
Ex 2
Identify congruent triangles.
Why are they congruent? B D
70
3cm
110
5 cm E C A F
2cm G L H
70
110
5 cm
3 cm I
2 cm J K

14. Ex 3
By what rule are the following triangles congruent? 90 30 90 30

15. Ex 4 A B C E D
By what rule is

16. is the perpendicular bisector of
Ex 5
is the perpendicular bisector of
By what rule are the triangles congruent? A C B M

17. Ex 6
bisects R T S U
By what rule are the triangles congruent?

18. find the measure of angle CB C A’ B’ C’
Ex 7
3 .Triangle ABC is congruent to triangle A’B’C’. If angle C is represented by 2x -10 and angle C’ is represented by 3x – 40,
find the measure of angle C