Geo.11.05.15.sec.3­7.notebook
November 05, 2015
Warm Up
1. Rotate the triangle ABC 270° counterclockwise. Give the coordinates of the image.
2. Now translate the triangle A'B'C' ( 1, ­2).
Give the coordinates of the image.
A (­5, 2)
A'
A''
B (­4, ­4)
B'
B''
C (2, ­ 6)
C'
C''
Dilation-- an enlargement
or reduction of a figure
Enlargement -- gets bigger
Reduction -- gets smaller
Geo.11.05.15.sec.3­7.notebook
November 05, 2015
Scale Factor -- a positive number
that is multiplied by the coordinates
of a shape's vertices
If the scale factor is greater than 1 --> enlargement.
If the scale factor is less than 1 --> reduction.
True or False?
A dilation is an isometry.
The preimage and image of a dilation are ______________ figures.
Geo.11.05.15.sec.3­7.notebook
which one shows a dilation?
November 05, 2015
Geo.11.05.15.sec.3­7.notebook
November 05, 2015
# 1 Scale Factor: 3
A(-3, 1)
B(-1, 4)
C(1, 4)
D(3, 1)
­9 3
­312
3 12
9 3
#6
Scale factor 1/2
A(­4,12)
B(6, ­2)
C(­14, ­2)
Geo.11.05.15.sec.3­7.notebook
# 7
November 05, 2015
Find the scale factor.
A(­3, 2)
A'(­10.5,7)
B(1,2)
B'(3.5,7)
C(1,­3)
C'(3.5,­10.5)
D(­3,­3)
D'(­10.5,­10.5)
9°
62
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
29°
0
1
2
3
4
5
Geo.11.05.15.sec.3­7.notebook
November 05, 2015
29°
247
HW #32
p. 169­171
(5 ­ 12, 20,21,33­40)
Geo.11.05.15.sec.3­7.notebook
# 4 Scale Factor: 2
A (-1,7)
B (1, 7)
C (5, 5)
D (5, 1/2)
E (1, -3)
F (-1, -3)
G (-5, 1/2)
H (-5, 5)
November 05, 2015