Warm-up

1
Warm-up
Solve the proportion.
3. The ratio of the sum of the exterior angles
of a regular polygon to the sum of the
interior angles is 13. Identify the polygon.
2
Lesson 7-3 Similar Polygons
Two polygons are similar if their vertices can be
paired so that
(1) Corresponding angles are congruent.
and
(2) Corresponding sides are in proportion.
(Their lengths have the same ratio.)
3
polygon ABCD
polygon ABCD
( is similar to )
From the definition of similar polygons, we have
Congruent Corresponding Angles
?A ? ?A
?B ? ?B
?C ? ?C
?D ? ?D
4
polygon ABCD polygon ABCD
From the definition of similar polygons, we have
Proportional Corresponding Sides
5
15
40
scale factor - the ratio of the lengths of two
corresponding sides.
The scale factor of polygon ABCD to polygon
ABCD is .
6
Ex 1.)
polygon RSTU polygon ABCD
Find
a. their scale factor
b. the values of x, y, and z.
c. the ratio of the perimeters
7
Ex 2.) ?ABC ?JKL. Solve for x and y.
8
HOMEWORK 34

• pages 250-252
• 1-27 all, 34