Geometry NOTES
Date: ________
Lesson 7-2: Similar Polygons
Similar Polygons:
~
- same shape, different size
- Corresponding angles are ≅.
- Corresponding sides are in proportion
Compare angles:
A  X,
Compare ratios of sides:
AB 6
 2
XY 3
B  Y
CD
9

2
ZW 4.5
C  Z
BC 8
 2
YZ 4
D  W
DA 4
 2
WX
2
Because corresponding sides are proportional AND corresponding angles are
congruent, ABCD ~ XYZW.
Try These! Determine if the figures are similar or not. Support your reasoning.
1.
Rectangles:
2.
Pentagons:
3.
Triangles:
Similarity Ratio / Scale factor : the ratio of the lengths of corresponding sides in similar figures.
1. What is the scale factor of the triangles?
Write the similarity statement.
2. ΔRST ~ ΔUVW. What is the scale factor?
What is the value of x?
.
3.
∆ABC ~ ∆EFG; Find EF.
4.
Quad PQRS ~ Quad LMNO ; Find NO
5.
∆ XYZ ~ ∆EFD. Find the value of x.
6. LMNO ~ RQTS. Find the value of x.
7.
a. Find the value of x.
b. Find the value of y.
8. You make a scale drawing of a tree using 5 inches = 27 feet.
If the tree is 67.5 feet tall, how
tall is the scale drawing of the tree? Write and solve a proportion.
HOMEWORK: pgs. 468 – 470 # 1-4, 10-16, 19-26