Transcript Rotation Rules

Blue Day – 1/16/2015
Gold Day – 1/20/2015

Find the Rule – Use your yellow cheat
sheet from last class
1. M (4,2) was rotated to M’(-4,-2)
2. A (-3,7) was rotated to A’(7,3)
3. P (1,5) was rotated to P’(-5,1)




Friday, 1/23/2015 is the last day for
progress report grades.
Missing grades must be turned in by
Tomorrow!!
Transformations Unit test 1/29/2015 &
1/30/2015
Today we will continue transformations
 Dialations
Translation, Rotation, and Reflection all
change the position of a shape, while the
size remains the same.
The fourth transformation that we are
going to discuss is called dilation.
DILATION
Dilation changes the size of the shape
without changing the shape.
When you go to the eye doctor, they
dilate you eyes. Let’s try it by turning off
the lights.
When you enlarge a photograph or use a
copy machine to reduce a map, you are
making dilations.
Enlarge means to make a shape bigger.
Reduce means to make a shape smaller.
The scale factor tells you how much
something is enlarged or reduced.
Notice each time the shape transforms the shape
stays the same and only the size changes.
200%
50%
ENLARGE
REDUCE
Look at the pictures below
Dilate the image with a scale
factor of 75%
Dilate the image with a scale
factor of 150%
A scale factor describes how much the figure is
enlarged or reduced.
For a dilation with scale factor k, you can find
the image of a point by multiplying each
coordinate by k: (a, b)  (ka, kb).
k > 1 is an enlargement, or expansion.
0< k < 1 is a reduction, or contraction.
Copy the figure and the center of dilation P.
Draw the image of ∆WXYZ under a dilation
with a scale factor of 2.
Step 1 Draw a line through
P and each vertex.
Step 2 On each line,
mark twice the
distance from P to the
vertex.
Step 3 Connect the
vertices of the image.
W
’
X’
Y’
Z’
Apply the dilation D to the polygon with the
given vertices. Describe the dilation.
D: (x, y) → D’(3x, 3y)
A(1, 1), B(3, 1), C(3, 2)
A’ (3, 3), B’ (9, 3), C’ (9,6)
scale factor 3
B. Apply the dilation D to the polygon with the
given vertices. Describe the dilation.
D: (x, y) → 3 x, 3 y
4
4
P(–8, 4), Q(–4, 8), R(4, 4)
P’(-6, 3), Q’ (-3, 6), R’ (3, 3)
scale factor 3/4