Question about homework?

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7.3 Proving Triangles Similar

Related Topic

• Remember we had to prove triangles congruent? Proving triangles similar is similar to proving triangles congruent but different

• The theorems to prove triangles similar are different

Postulate 7.1 Angle-Angle similarity (AA~) Postulate

• If two angles of one triangle are congruent to two angles of another triangle, then the triangles are similar

R

T

S L

P

M

PLMTRS ~

Theorem 7.1 Side-Angle-Side Similarity (SAS~) Theorem

• If an angle of one triangle is congruent to an angle of a second triangle, and the sides including the two angles are proportional, then the triangles are similar

• Examples:

Notice the difference

Theorem 7.2 Side-Side-Side (SSS~) Theorem

• If the corresponding sides of two triangles are proportional, then the triangles are similar

• Examples:

Are the triangles similar? Why? Write the similar statementW

R

SV

B

45

45

Are the triangles similar? Why? Write the similar statementP

Q R Z

X

Y3

8

4

6

If the triangles are similar, find DE

A

C

BD

E

10 12

16

24

18

Vocabulary

• Indirect measurement – You use similar triangles and measurements to find distances that are difficult to measure directly

Example of indirect measurement

Homework/Classwork

• Pgs 385-387 #1,2, 4-20, 24-27, 32