Hi, Mrdavid445.

Since the rotation is about the z-axis, we are rotating the point (4,3,1) in the plane z=1. Since the rotation occurs in a plane, we can use the two-dimensional counterclockwise rotation matrix

,

where is the angle of rotation - see Rotation matrix - Wikipedia, the free encyclopedia. If we multiply the vector (T is the transpose) times the rotation matrix (after plugging in a value for ) we will obtain the new x and y coordinates for the rotated point. Since the rotation is in the plane z=1, the z coordinate will still be 1.

Does that answer your question?

Good luck!