math.cos reveals OS
part1: background / obsolete code?
I can't find the old ticket, but it's probably relevant- it was about the implementation of higher math functions
However (unless I made a mistake), I see no difference in these returned values in a vanilla ESR60, or FF60 thru to 66 as compared to Tor Browser. So I am not sure if the old patch is still required, or has even been rebased.
part2: math.cos Windows: FF vs TB
results: see attachment test: https://thorin-oakenpants.github.io/testing/ (for as long as I leave it there)
I do not know if that ticket/patch causes this, but there is a difference between TB vs FF for no discernible reason (e.g Linux doesn't differ between FF and TB)
Look at the first result. FF:
minus 0.374... vs TB
part3: math.cos reveals platform
finally, to the meat and potatoes. See attachment. I'm using math.cos because it always returns a value between -1 and 1 (i.e no NaN or Infinity). The following tests show that, so far, the last four values can be used to detect windows or Linux, and so far one Android major version (v5.*). I am fully expecting the first four value to betray other Android and macOS/macOS X. My testing is incomplete, but enough to prove os FP'ing