Re: what calculator do you use?
On Mon, Jul 13, 2020 at 09:06:17PM -0400, The Wanderer wrote:
> Based on a bit more digging, apparently calc does also have an atan()
> function, which produces the arctangent of its argument; atan(1)*4 gives
> 3.14159265358979323848. Oddly, that last digit is not the same as what
> 'bc -l' gave from '4*a(1)' in Greg's demonstration; it looks like
> atan(1) gives a value which is off in the very last displayed decimal
> place from what Greg gave. I suspect that there is display rounding
> involved on one side or the other.
One doesn't expect the last few digits of precision to be... precise. ;-)
When using bc with its default scale of 20, for most calculations
you'll end up with however much precision you *actually* want (say,
5 or 6 digits) after you round the final value. It's not intended
to be absolutely correct to 20 digits. It simply *uses* 20 digits in
all of its intermediate calculations. As I pointed out earlier, the
rounding errors accumulate.
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