Thanks for the bug report. Sorry Maxima gets the wrong answer here.
I'm pretty sure that the problem is that Maxima simplifies (655/656)^n ->
655^n/656^n (which is correct), then tries to evaluate that expression for
various float values of n. For n>109 or so, the intermediate values are IEEE
Inf's, and so the quotient is an IEEE NaN. Unfortunately, Maxima doesn't
know how to handle IEEE Inf/NaN, and even worse, does not signal an error to
indicate this.
It is also embarrassing that Maxima can't solve (655/656)^n=1/2
symbolically.
Could you please submit this bug to our bug tracking system? (Use
bug_report()$ for instructions.)
Thanks,
-s
On Tue, Jul 22, 2008 at 8:30 AM, Tawny Owl <tow_force at hotmail.com> wrote:
> I am using Maxima 5.15.0 under Windows.
>
> find_root((655/656)^n = 0.5, n, 1, 1000) gives 114.8, which is completely
> wrong.
>
> Fortunately, I checked the answer (always a good habit, I know!).
>
> Either of the following expressions give the correct answer, which is 454.4
>
> find_root(float(655/656)^n = 0.5, n, 1, 1000);
> float(log(0.5)/log(655/656));
>
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