Bottom line is that $sin(180).deg should be 0, it's not - therefore it's a bug. Doesn't matter
why it's wrong, how wrong it is, or how easy it is to work around. A bugs a bug and should be fixed.
While some other programming languages can sometimes come up with an accuracy-based issue of something like 1.01e-16 or something, mIRC's limited accuracy in calculations means there's no reason it should be experiencing these issues and more importantly is apparently raising that innaccuracy by many orders of magnitude in order to get the answer it returns.
Also it would be nice if the documentation actually stated what the .deg property does. I'm sure people can figure out it's short for degrees but they wouldn't know from the helpfile if it takes degrees as a parameter, returns degrees, or both. I know it says in
versions.txt but
a) nobody seems to read it and
b) it's not in the shortened
versions.txt distributed with mIRC anymore.