On 3/21/11 12:01 PM, Jaime Villate wrote:
> On Mon, 2011-03-21 at 14:25 +0100, Michael Kogan wrote:
>> implicit_plot(1=integrate(1/sqrt(1+(1/z-1)*x
>> +(z^2-1)*y),z,0,1),[x,-5,5],[y,-5,5]);
>>
>> Output
>>
>> Maxima encountered a Lisp error:
> Hi,
> the problem is not with implicit_plot, but with integrate which cannot
> solve that integral. Even using one of the numerical methods in Maxima
> that integral will fail, because in z=0 the term 1/z gives you an
> overflow.
Agree with the part about maxima not being able to do the symbolic
integration. The integrand is the square root of a cubic, which leads
to elliptic integrals, which maxima doesn't know how to do.
However, the 1/z term is no problem. quad_qags easily evaluates the
integral once values for x and y are substituted. I thought that
perhaps changing the call to implicit plot to something like
f(x,y):= quad_qags(<integrand>,z,0,1)[1];
implicit_plot(f(x,y)-1,[x-5,5],[y,-5,5])
would work, but it doesn't.
Ray