# Warm UP x Given that the following two pentagons are similar, find x.

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Warm UP x Given that the following two pentagons are similar, find x.
8 12 x 4 14 4 5 6 7 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
B 21 13 9 27 C 7 A D 39 F

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
B 12 8 C 4 A D 6 F

SAS Similarity Postulate
∆ABC ~ ∆FED

AAA Similarity Postulate
Two triangles are similar if two pairs of corresponding angles are congruent

AA Similarity Postulate
B C A D 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.

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