Geom9.5.notebook
January 23, 2014
Geometry
Ch.9 Notes Page 12
P12 9­5 Dilations
Apr 12­6:29 AM
Dilations
Dilation: A transformation whose preimage and image are Similar. (Larger or Smaller) ***It is not an Isometry
All Sides are proportional and Corresponding Angles are Congruent
Every dilation has a Center and Scale Factor (n):
If n is > 1, it is an Enlargement
If n is between 0 and 1, it is a Reduction
May 9­6:58 AM
1
Geom9.5.notebook
January 23, 2014
Dilations
Scale Drawings:
Maps
Blue Prints
Dilations are Similar Figures
(Make Pictures Bigger or Smaller)
May 9­2:35 PM
Dilations
Scale Factor (How Big or Small)
Center of Dilation (Where to Start Counting)
Use the Origin
SF = 1/2
CoD = (0, 0)
May 9­2:35 PM
2
Geom9.5.notebook
January 23, 2014
Example
SF = 2
CoD = (0, 0)
May 9­2:36 PM
The blue triangle is a dilation image of the red triangle.
Describe the dilation.
May 9­6:58 AM
3
Geom9.5.notebook
January 23, 2014
Scale Models: The packaging lists a model car's length as 7.6 cm. It also gives the scale as 1 : 63.
What is the length of the actual car?
May 9­6:58 AM
May 9­7:01 AM
4
Geom9.5.notebook
January 23, 2014
In Class
9­5 Letter Activity
Terms:
Dilation, Enlargement, Reduction
Apr 12­6:29 AM
May 9­2:47 PM
5