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On Wed, 6 Jul 2005, Aubrey Jaffer wrote: > | Thereby hypothetically: (presuming sufficient numerical precision) > | > | (tan pi/2) => 0 > >An exact zero? That is just wrong. No, actually it's more right than we expect computation to get. If pi/2 can be an exact number in the representation used by the scheme system, an exact zero is precisely the correct response to (tan pi/2). That said, tan isn't one of the functions that is required to return an exact result given exact arguments, so even if pi/2 is exact in the number representation, we still aren't *required* to return the exact zero, even though it's true. In the usual case, where the numeric representation does not allow pi/2 to be expressed as an exact number, then we have an operation on an inexact number and we *must* return an inexact result. Bear