Download 8 - My CCSD

8.5 Proving Triangles are Similar
Objectives:
(1) The student will be able to use similarity
theorems to prove that 2 triangles are similar.
(2) The student will be able to similar triangles to
solve real-life problems.
Toolbox:
Summary:
Side-Side-Side (SSS) Similarity Theorem:
If the lengths of the corresponding sides
of 2 triangles are proportional, then the
triangles are similar.
Side-Angle-Side (SAS) Similarity Theorem:
If one angle of one triangle is congruent to
an angle of a second triangle and the lengths
of the sides including these angles are
proportional, then the triangles are similar.
Examples:
1. Write a paragraph proof.
Given: ∆AEC ~ ∆GFH; DC = FH
Prove: ∆BCD ~ ∆GHF
2. In the figure, AC= 6, AD = 10, BC = 9, and
BE = 15. Describe how to prove that ∆ACB is
similar to ∆DCE.
3. At an indoor climbing wall, a person whose
eyes are 6 ft from the floor places a mirror 60
ft from the base of the wall. They then walk
backwards 5 ft before seeing the top of the
mirror. Use similar triangles to estimate the
height of this wall.
4. Which of the following 3 triangles are similar?