I think there may be a little correction, as shown in the image the matrix A_rotation is rotation by 90 degrees anticlockwise and not the clockwise.

It depends on what coordinate system is used. The assignment doesn’t specify that.

I’ll notify the staff that this either needs an update or clarification.

Thanks!

The matrix given in Example 3 seems to be correct if using a right-hand coordinate system (the mathematical standard with the origin in the lower-left corner).

Reference this image from Wikipedia:

Then clockwise rotation is -90 degrees, and computing the rotation matrix gives the matrix shown in the notebook - because sin(-90) = -1 and cos(- 90) = 0.

Thank you, I got it, I was little confused.