Use left/right arrows to page through! Presumed knowledge: The definitions of sine and cosine using the unit circle. A vector has a direction and a length.
In many situations, there are easier ways to rotate stuff in Scratch. However, if the Cartesian coordinates of objects are known, then this is an easy way to rotate the objects. Also, this is needed when using 3D rotation matrices. I used this when rotating the petals of the Quartic Bézier flower: http://scratch.mit.edu/projects/11525308/ For an actual matrix-description, see Wikipedia - Rotation matrix: http://en.wikipedia.org/wiki/Rotation_matrix
