Calculating Angle from Coordinates.

**Edit:** Hm. Possibly this would be better suited to the general forum area, but I missed that when scanning through the sections. Please could it be moved there, if deemed more suitable for that area? Sorry to be a bother!

Hi all!

I recently recieved an assignment from my college (I'm on a BTEC IT Course), to create a program in Delphi designed to aid high school students in learning angles and coordinates and the like.

Now, the trouble with this is that I actually do not know the equations for the program I am supposed to be making, and so I came here for some help :)

I created a quick example image in Photoshop, to help explain what I require:

http://www.prelogic.net/eg_1.gif

Assuming that the red dot is X, the blue dot is Y, and 0 degrees is straight up, I require some sort of equation that will calculate the angle in degrees to make point X face point Y. So in the example above, it would be 45 degrees.

The program I have been told to make has to provide a simple graph, like the one above, and allow the user to plot two points, again like above. It would then calculate the angle and output it.

I hope I have made myself clear enough, and I hope I chose the correct forum section... I couldn't find an angles/degrees specific forum, so Trigonometry seemed to be the next best thing.

Thanks for reading, and thanks to any who help or attempt to ;)

Dave

PS: I have absolutely no idea how easy/hard this is - I'm extremely bad at maths! :(