news:441ea0bb@news.povray.org...
> >>"atan2(A,B): Arc-tangent of (A/B). Returns the angle, measured in
> >>radians, whose tangent is (A/B). Returns appropriate value even if B is
> >>zero. Use atan2(A,1) to compute usual atan(A) function."
> >
> >
> >>Um... yeah, OK... so why does atan2(0, 0) give we a fatal parse error?
> >
> >
> >   Because the result is not defined. You are basically asking the
> > direction of a zero vector, which has none.
>
> I just thought the whole point of using atan2 was to _avoid_ divide by
> zero errors.
>
> Sure, if the vector has a length of zero it has no defined direction.
> OTOH, I would imagine in most cases it just wouldn't *matter* what
> number the function returns in this case - just so long as it returns
> something, rather than an error...
>
> Oh well.

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