Light A is directly over the shoulder of the camera and light B is 180 degrees to the subject's left. There is a shadow cast behind him towards the right.
Light A is 45 degrees to the right of the camera and light B is 180 degrees to the right of the subject. There is a shadow cast to the subject's left.
Light A is 45 degrees to the left and light B is 180 degrees also to the left of the camera. a shadow is cast to the right.
Light A is 180 degrees to the left and light B is over the shoulder of the camera. a shadow is cast behind the subject to the right.
Light A is directly on the backdrop on the right while light B is 180 degrees on the left. There is no shadow.