1. Similar Triangles
Similar Triangles – Two triangles are similar if and only if there is a correspondence between their vertices such that their corresponding sides are proportional and their corresponding angles are equal.
If ABC~DEF, then
AB/DE = BC/EF = AC/DF and
A= D,  B=E,  C=F.

2. Similar Triangles Angle-Angle (AA) Similarity Postulate
If two angles of one triangle are congruent to two angles of a second triangle, then the triangles are similar.
Side-Side-Side (SSS) Similarity Postulate
If the measures of the corresponding sides of two triangles are in proportion, then the triangles are similar.

3. Similar Triangles Side-Angle-Side (SAS) Similarity Postulate
If an angle of one triangle is congruent to an angle of another triangle, and the lengths of the sides including those angles are in proportion, then the triangles are similar.
Theorem 6.3
Similarity of triangles is reflexive, symmetric, and transitive.

4. In the figure, OW = 7, BW = 9, WT = 17. 5, and WI = 22. 5
In the figure, OW = 7, BW = 9, WT = 17.5, and WI = Determine which triangles in the figure are similar. I
Answer:
Example 3-1c

5. ALGEBRA Given and CE x + 2, find AC and CE.
Answer:
Example 3-2d

6. INDIRECT MEASUREMENT On her trip along the East coast, Jennie stops to look at the tallest lighthouse in the U.S. located at Cape Hatteras, North Carolina. At that particular time of day, Jennie measures her shadow to be 1 feet 6 inches in length and the length of the shadow of the lighthouse to be 53 feet 6 inches. Jennie knows that her height is 5 feet 6 inches. What is the height of the Cape Hatteras lighthouse to the nearest foot?
Answer: 196 ft
Example 3-3d