1. Chapter 7 Lesson 2: Similar Polygons
Geometry CP
Mrs. Mongold

2. Similar Polygons
Definition: Polygons that have exactly the same shape but not necessarily the same size.

3. ~ Symbol for Similarity
The symbol used in statements for similarity is the tilda ~

4. Steps to determine similarity
1. Make sure the polygons are the same shape, both triangles, quadrilaterals, pentagons, etc and all angles are congruent.
2. Match up corresponding sides, the longest sides are a pair, the shortest sides are a pair, and everything in between.
3. Write scale factors in simplest form for EVERY pair of corresponding sides.
4. Determine similarity, if all scale factors are equal then the shapes are similar, if one is different they are not!

5. Practice Problem Determine if the figures are similar or not. 8 8 5 410 10 3 4 5 6

6. Follow the Steps 1. Are they the same shape? 2. Match up the sides.
Yes, Pentagons
2. Match up the sides.
10 with 5, 8 with 4, and 6 with 3
3.Write scale factors in simplest form.
10/5 = 2, 8/4 = 2, and 6/3 = 2
4. Determine similarity.
The pentagons are similar because all scale factors are equal

7. More Practice on pg 14 and 15 Pg 14 1. Yes similar, SF 5/8
2. No not similar because the angles are not the same
3. Yes similar, SF ½
4.Yes similar, SF 5/4
Pg 15
1. SF 2/3, x = 6, y = 15
2. SF 2/1, x = 2.25, y = 5
3. SF 2/3, x = 27, y = 15
4. SF 4/3, x = 24, y = 27

8. Homework Due Tomorrow
Pages 16 and 17 (skip #5 on pg 17)