Sin and cos functions wrong?

[iBeatz]

I've been doing an angle-based movement project, and haven't really done anything major with angles in GScript until now.
When I use a variable which is equal to 180 and take the sine of it using sin(), instead of echoing 0 for the sine value of 180 (which I know it should), it echoes a value of -0.801.
The same goes for the cosine value of 180. It echoes a value of -0.598 instead of -1.

Any reason for this, or is there something wrong with the functions?