7.2 Similar Polygons - Henry County School...

7.2 – Similar Polygons

Learning Target 1: To be able to use properties to identify similar polygons. Learning Target 2: To be able to solve proportions using the properties of similar polygons.

• Similar: figures that have the same SHAPE but not necessarily the same size.

• Similar Polygons have… • corresponding angles that are congruent • corresponding sides that are proportional

Name the Corresponding Angles… (CONGRUENT)

Name the Corresponding Sides… (PROPORTIONAL)

Similar Polygons…

Similarity Statement…

Scale Factor…

• Scale Factor: The ratio of the lengths of the corresponding sides of 2 similar polygons.

ABC XYZ

A

B

C

6

X

Y

Z

3

Given: 6

23

3 1

6 2

ABC to XYZ is

XYZ to ABC is

Scale Factor…

Are We Similar??

Corresponding angles congruent? Corresponding sides proportional? If so… What is the scale factor? Write a similarity statement.

Are We Similar??

Corresponding angles congruent? Corresponding sides proportional? If so… What is the scale factor? Write a similarity statement.

Scale Factor…

• When polygons are similar, the scale factor can be used to find the values of variables.

Determine the scale factor. Then set up a proportion and solve for the unknown variable.

Scale Factor…

Determine the scale factor. Then set up a proportion and solve for the unknown variable.

Scale Factor…

Determine the scale factor. Then set up a proportion and solve for the unknown variable.

Perimeters of Similar

Polygons…

If ABCDE ~ RSTUV… find the scale factor of ABCDE to RSTUV and the perimeter of each polygon.

Perimeters of Similar

Polygons…

Perimeters of Similar

Polygons…

If ABCDE ~ RSTPQ… find the scale factor of ABCDE to RSTPQ and the perimeter of each polygon.

Pg. 469

#1, 2, 12 – 15,

18 – 21, 23, 24,

35, 36

Homework