1. 9.4 Rotations January 28, 2013
Bellwork
Please remove your snowflake off the door and take it home.
4. Find the point C on the x­axis so AC + BC is a
minimum for A(2, 5) and B(7, 3).
Jan 28­7:35 AM
HW pg. 602 #4­20 evens 1

2. 9.4 Rotations January 28, 2013
9.4 Rotations
Center of Rotation: figure is turned about a fixed point
Angle of Rotation: rays drawn from center of rotation to
a point and its image
Jan 28­8:00 AM
HW pg. 602 #4­20 evens 2

3. 9.4 Rotations January 28, 2013
Rules for Rotations about the Origin:
90 : (­y,x)
180 : (­x,­y)
270 : (y,­x)
Jan 28­9:03 AM
HW pg. 602 #4­20 evens 3

4. 9.4 Rotations January 28, 2013
Jan 31­7:48 AM
HW pg. 602 #4­20 evens 4

5. 9.4 Rotations January 28, 2013
Rotation Matrices
[1
90 : 0 ­1
0 [ 270 :
[ 0
­1
1
0 [
[ 0
180 : ­1 0
­1 [ [ 0 0 [
360 : 1
1
Jan 28­9:01 AM
HW pg. 602 #4­20 evens 5

6. 9.4 Rotations January 28, 2013
Rotation Theorem: A rotation is an isometry.
Jan 28­10:57 AM
HW pg. 602 #4­20 evens 6

7. 9.4 Rotations January 28, 2013
HW pg. 602 #4­20 evens
Jan 28­12:30 PM
HW pg. 602 #4­20 evens 7