Re: Tough problem...

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.

I'm no expert here, and I dont quite get where the i comes from, but
if it's an loop index, couldn't you do something like this:

var
i: integer;
j: double;
begin

j:= start_value;
for i:= start_value to end_value do
begin
compute sin(j*arg)
j:= j + 1;
if j > TWO_PI then
j:= j - TWO_PI;
end;
end;

Certainly not perfect, but should hold on to more precision than using
sin(i*arg) straight up, i think?

That won't work if arg has a fractional part.

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