Flash angles

I… I can’t take it anymore. For a long time I’ve been trying to understand how Flash manage his internal angles, with little success.

There was one or two places pointing out how to convert said angles to radians, but none explained what the hell negative numbers were doing so often in my sprite’s rotations.

The last drop happened a couple of minutes, when I tried to get the sin from the difference between two “flash angles” and the result was 6 x 10 to the 17. Yeah, you heard it right. The result from a Math.sin function had SEVENTEEN ZEROES.

So, I’m here looking for enlightenment. The angles goes from 0 to -180 and then from 180 to 0 again, instead of from 0 all the way to 360, but why the hell is it this way? What is this system good for?
And how does those values achieve such obscenities with the common trigonometric functions?