Warm UP• Given that the following

two pentagons are similar, find x.

x4

6

7

5

12 8

414

10

Objective• SWBAT use the AAA, SAS

and SSS similarity postulates to decide which triangles are similar and find unknowns.

Homework

• P. 433 – 434: # 5 – 9, 12 – 19

Congruence vs. Similarity

• The match of the century!

• Who will win?

Congruence vs. Similarity

• Congruence implies that all angles and sides are equal/identical whereas...

Congruence vs. Similarity

•Similarity implies that only the angles are congruent and the sides are proportional

Congruence vs. Similarity

• What can be congruent?

• What can be similar?

Back to Triangles

• Since we talked about congruent triangles so much, we should mention similar triangles.

Back to Triangles• How could triangles be

congruent?

• SSS

• SAS

• ASA

AAS

HL

SSS Similarity Postulate

• Two triangles are similar if all three pairs of corresponding sides are proportional.

SSS Similarity Postulate

A

B

C D

E

F7

219 2713

39

SSS Similarity Postulate

•∆ABC ~ ∆EDF

SAS Similarity Postulate

• Two triangles are similar if two pairs of corresponding sides are proportional and the included angle is congruent

SAS Similarity Postulate

A

B

C D

E

F4 6

8 12

SAS Similarity Postulate

•∆ABC ~ ∆FED

AAA Similarity Postulate

• Two triangles are similar if two pairs of corresponding angles are congruent

AA Similarity Postulate

A

B

C D

E

F

AA Similarity Postulate

•∆ABC ~ ∆FED

Example

•∆APE ~ ∆DOG. If the perimeter of ∆APE is 12 and the perimeter of ∆DOG is 15 and OG = 6, find the PE.

Conclusion

•Congruence vs. Similarity

•AAA~

•SAS~

•SSS~

Practice 10-2•Answer Example sets 2 and 3.

•Be sure to include the similarity statement.