1. 8.3 – Similar Polygons Two polygons are similar if:
-their corresponding angles are congruent
-their corresponding sides are proportional
~ “similar to” R U I L P S A G

2. <A <G <P <S <I <R <L <U
Angles are Congruent Sides are Proportional
<A <G
<P <S
<I <R
<L <U R U I L P S A G
PILA~SRUG

3. Are the two triangles similar? If so, write the similarity statement.5 3
30º 10 8 S P 4
60º G 6 U
SIP~RGU

4. Scale Factor – the common ratio of the corresponding sides of similar polygons5 3
30º 10 8 S P 4
60º
Find the scale factor of PSI to URG G 6 U

5. Are the two triangles similar? If so, what is the scale factor?4 8 5
40º 12 8
Not similar!
50º 6

6. Given that PILA~SRUG, determine the values of a, b, x and y.9 R U 3 I L
20º bº y 1 P x S 12
60º 2 6 A aº G

7. ABC and ABD are both isosceles triangles with AB = AC and AD = BD.
Are the corresponding angles congruent?
Write a similarity statement. A
70° B D C

8. Given that QP // ON, Prove that the triangles are similar.
-Because QP // ON, there are 2 sets of corresponding angles.
-The triangles share the third angle at M, so corresponding angles are congruent
- Since , corresponding sides are proportional! Q 6 12 O 4 3
70° M P 4 2 N

9. E F 2 B A D C H G 7/2 The figures are both squares. Are they similar?
4 to 7
What is the scale factor?
What is the ratio of their perimeters?
Find the perimeter of ABCD 8
8/14 = 4/7
Find the perimeter of EFGH 14 E F 2 B A D C H G
7/2

10. So…
Theorem 8.1 – If two polygons are similar, then the ratio of their perimeters is equal to the ratio of their corresponding sides.