What is the rule for a 90 degree clockwise rotation about the vertex?

A 90-degree clockwise rotation about a vertex involves moving each point in the shape a quarter turn to the right around that vertex. For a point ((x, y)), the new coordinates after the rotation will be ((y, -x)) when considering rotation around the origin. If rotating around a different vertex, you first translate the shape so that the vertex becomes the origin, apply the rotation, and then translate back.