Bellwork
Solve the problem below and turn it in. Have your
homework out to check.
Solve for x.
2 x  3 4

x 1
5
(Note: Your answer will NOT be an integer!)
STUDENTS WILL BE ABLE TO
IDENTIFY PROPORTIONAL SIDES
AND CONGRUENT ANGLES OF
SIMILAR POLYGONS GIVEN A
DIAGRAM OR SIMILARITY
STATEMENT.
7.2 Similar Polygons
Ponder…

How are the two giraffes the same/different?
Similar Polygons (Defn)
Polygons that are similar are the
same ______
Shape but not necessarily
Size
the same_____!
Similar Polygons (Defn)
Two things must be true if two polygons are
to be similar ( )…their
1.
corresponding angles are congruent
2.
corresponding sides are proportional
Example 1

Are the two figures similar? If so, write a
similarity statement and justify.
Scale Factor (Defn)

The ratio that compares the lengths of the
corresponding sides of similar figures is called the
scale factor.
Example 2
The polygons below are similar.
1. Write a similarity statement.
2. Find DE and DF.
3. Find the scale factor from left to right.
Example

Billy is building a model of Chicago out of
toothpicks. If his model made the Willis tower 60
toothpicks tall, what is the scale factor?
 What
 The
do we need to know to solve
Willis tower is 1450 feet tall
 A toothpick is 2.5 inches long.
Example 3

The pair of polygons are similar. Write a
similarity statement, find PS and TS.
Ticket to Leave

If ABC~ DEC, find DE.
Homework

Pg. 392 # 1, 2, 4, 10, 14, 15, 19, 64, 68, 70