1. 9.4 Rotations January 31, 2011
Bellwork
4. Find the point C on the x­axis so AC + BC is a
minimum for A(2, 5) and B(7, 3).
HW pg. 602 #4­20 evens 1

2. 9.4 Rotations January 31, 2011
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
HW pg. 602 #4­20 evens 2

3. 9.4 Rotations January 31, 2011
Rules for Rotations about the Origin:
90 : (-y,x)
180 : (-x,-y)
270 : (y,-x)
HW pg. 602 #4­20 evens 3

4. 9.4 Rotations January 31, 2011
HW pg. 602 #4­20 evens 4

5. 9.4 Rotations January 31, 2011
Rotation Matrices
[1
90 : 0 -1
0 [ 270 :
[-1
0 1
0 [
[ 0 -1[
180 : -1 0
[ 0 0[
360 : 1
1
HW pg. 602 #4­20 evens 5

6. 9.4 Rotations January 31, 2011
Rotation Theorem: A rotation is an isometry.
HW pg. 602 #4­20 evens 6

7. 9.4 Rotations January 31, 2011
HW pg. 602 #4-20 evens
HW pg. 602 #4­20 evens 7