GT Geometry 3/2/11• Turn in CW/HW from

yesterday by the time the bell rings.

• Pick up a ditto and complete 1-6

#3.16 Geo. Drill 3/2/11• Given that the following two

pentagons are similar, find x.

x4

67

5

12 8

414

10

Geometry Drill

•Can you list the 5 ways to prove triangles congruent

Objective•Students will use the AA, SAS and SSS similarity postulates to decide which triangles are similar and find unknowns.

Congruence vs. Similarity

•Congruence implies that all angles and sides have equal measure whereas...

Congruence vs. Similarity

•Similarity implies that only the angles are of equal measure and the sides are proportional

AA Similarity Postulate

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

AA Similarity Postulate

A

B

C D

E

F

SAS Similarity Postulate

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

SAS Similarity Postulate

A

B

C D

E

F4 6

8 12

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

Example 1

•∆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

•AA

•SAS

•SSS

Classwork/Homework

•Page 433-434 5-19 skip 10, 11.