Let’s cal the pure counterclockwise rotation of the matrix
cos (theta) −sin (theta)
sin (theta) cos (theta) as , and the "undo" of the pure
rotation is
cos (−theta) −sin (−theta)
sin (−theta) cos (−theta) as −theta.
a. simplify
cos (−theta) −sin (−theta)
sin (−theta) cos (−theta)
b. what would you get if you multiply to −theta?
c. write the matrix if you want to rotate

2
radians counterclockwise.
d. write the matrix if you want to rotate

2
radians clockwise.
e. write the matrix if you want to rotate

6
radians counterclockwise.
f. write the matrix if you want to rotate

4
radians counterclockwise.
g. if the point
is the image of

4
radians counterclockwise rotation, find the starting point
x

h. if the point
1
2

2
is the image of

6
radians counterclockwise rotation, find the starting point
xy