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
Similar Polygons…
Similarity Statement…
Name the Corresponding Angles… (CONGRUENT)
Name the Corresponding Sides… (PROPORTIONAL)
Scale Factor…
• Scale Factor: The ratio of the lengths of the
corresponding sides of 2 similar polygons.
Given: ABC
A
XYZ
Scale Factor…
6
ABC to XYZ is  2
3
C
Y
6
3
B
X
Z
3 1
XYZ to ABC is 
6 2
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…
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…
If ABCDE ~ RSTPQ… find the scale factor of
ABCDE to RSTPQ and the perimeter of each polygon.
Homework 
Pg. 469
#1, 2, 12 – 15,
18 – 21, 23, 24,
35, 36