Re: Tough problem...

The solution is not to pass a large argument in the first place,
which can often be achieved if you're dealing with a "physical"
problem (in opposition to "mathematical" problem). The "how" will
depend on the problem, and can range from separating values
(number of rotations + angle instead of an absolute angle) to
transforming the math (using trigonometric formulas, quaternions,
etc.), using a converging series or introducing a well chosen
approximation.

This situation occurs in FFT, when the length of the FFT goes in to
million of points. The sin and cos functions become inaccurate when
the i in sin(i*arg) goes in to millions.

Try something like this:

Angle := 0;
for I := 0 to 100000 do
begin
MySin := Sin(Angle);

Angle := Angle + arg;
while Angle >= 2 * Pi do
Angle := Angle - 2 * Pi;
end;

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