7.3 Proving Triangles Similar
Proving triangles similar is like proving triangles congruent! We have some theorems
and postulates that we can use to say triangles are similar.
Postulate 7-1: Angle-Angle Similarity (AA~) Postulate
Theorem 7-1: Side-Angle-Side Similarity (SAS~) Theorem
Theorem 7-2: Side-Side-Side Similarity (SSS~) Theorem
These are the only theorems/postulates that you
can use to say or prove that triangles are
similar!!!
Explain why the triangles must be similar. Write a similarity statement.
Are these triangles similar? If ‘yes’, write a similarity statement and find
DE.
The following triangles are similar by what theorem or postulate? Then
find x.
In sunlight, a cactus casts a 9-ft shadow. At the same time, a person 6ft
tall casts a 4-ft shadow. Use similar triangles to find the height of the
cactus.
Write a Two-Column Proof!! (Hint: Use the properties of Proportions to get you started!!)
Given: RT  TQ  MT  TS
Prove: RTM ~ STQ
Homework #19
Page 385 #1-3, 6-18 even, 24, 28, 30-38 even