[Gmercer]

I'm having a lot of trouble coming up with an algorithm on programming an arcade drive on a single joysick. We're using one joystick for our shooter, so our other one must drive the entire robot, here is what i know:

For both(joysticks):

Y values:
Up is -1
Down is 1

X values:
Left is -1
Right is 1

i know there is something to do with triangles, but i'm not quite sure. Any help / links are really appreciated, thanks!