Here's the situation i have:
I have a ball (2D), and an arrow.
In the game, the player touches the screen, and drags their finger. When the finger is lifted, the game subtracts the two vectors (finger down, finger up) and launches the ball in the opposite direction of the invisible "line" drawn by the finger.
I want to have a pointer arrow show the direction the ball is going to fly in.
I want the arrow to circle around the ball, like a north arrow on a minimap for example, and show the direction the ball will fly.
How would I go about doing this?