Vedran's got a good point, as existing documentation for math.nan already says

"... Equivalent to the output of float('nan')."

so it does seem a bit redundant to say both, though I wonder if we should still be explicit since

>>> import math
>>> math.nan is math.nan
True
>>> float('nan') is float('nan')
False

so they don't have the exact same behavior.

Serhiy also has a good point, so maybe instead say that Math.nan/float('nan') is *generally* not equal to any other value?