sine of an angle in degree mode

[rflesch]

Of course, 90 deg is exactly a right angle, whereas a calculator cannot represent a right angle exactly by using radians.
So - the argument of the sine function of a right angle (in degrees!) is exact, but the algorithm that calculates the function value of this argument cannot be exact as far as I can see. I would assume that no algorithm in the known galaxy could calculate sin(180deg) exactly, because the value is a real number, i.e. "0.00000(...)". I would greatly appreciate if somebody could tell me if I am wrong here.