Hi Aaron,
see below.
Daniel
Aaron Fude wrote:
> Hi,
>
> I can't figure out how the precision and accuracy concepts work in
> Mathematica.
>
> A. First of all, what's the difference? (Is it only total number of
> digits vs digits after decimal?)
exactly, for a banker the accuracy makes sense, but the accuracy does
not make much sense for numbers near zero.
>
> B. Secondly, could someone talk through the logic of why.
>
> N[Tanh[100000] - 1]
>
> equals 0, while
>
> N[Tanh[100000``1] - 1]
>
> equals -3.*10^-86859;
100000``1 means the number is somwhere between 99999.5 and 100000.5,
the result must therefore be between:
{1.3803010643*10^-86858,1.8680343549*10^-86859},
no mistery here.
>
> C. On a related issue, how do I see Pi to a certain number of digits.
> I figured out this hack:
>
> 1``100 Pi
hi, we have N[Pi,100] for this
>
> D. And finally (for now) where can I read up on rules for "precision
> arithmetic". For example, my guess that
>
> Precision[1`10 + 1`100]
>
> ought to be 100-ish rather than 10-ish.
well, you add an inaccurate numer to a more accurate one and expect the
result to be accurate????
>
> Many thanks in advnce!
>
> Aaron
>
--
Daniel Huber
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