as often with gnumeric, you ( I ) think to have a good idea ... it's already in ...
there is a function 'sinpi' which calculates sin for multiples of 𝜋 to better accuracy. same for cos and tan, not for asin, acos, atan.
IMHO it's still considerable to change the results of sin(x*pi()), accounting pi() as a deputy / placeholder for 𝜋.
