Angle reflect in Cocos2d?

I am making a game in Cocos2d. I have a ball that will be shot at a flat surface (the top of the screen) how can I make it so the ball will travel, hit the surface, then reflect the angle and travel that direction? Does that make sense? Please tell me if it doesn't, and I will clarify. 开发者_如何学GoThanks!

EDIT:

Here's an illustration of what I want

Here

You could build the game using box2d (in cocos2d). Then you will have that "effect" for free.

Once you launch a ball at an angle, say 50 degrees, add (cos(50)*speed) to his X position, and (sin(50)*speed) to his Y position. When you detect the ball's y position has reached the surface's y position, just change the angle to -50.

But you must know that it only works if you want a reflection angle on a top surface, where it hits the top surface and bounces down.