On 2/18/08, Marco Carmosino <mogunus at gmail.com> wrote:
> Hello all. I am trying to find all points where two functions intersect,
> using maxima.
>
> These are my function definitions:
>
> (%i29) log2(x) := log(x)/log(2)
> (%i84) eq1 : y = 64*n*log2(n)$
> (%i85) eq2 : y = 8*n^2$
> (%i99) find_root([eq2,eq1],y,1,100);
find_root knows how to handle just 1 equation at a time.
(There is another function mnewton which can handle multiple
equations via Newton's method. But I don't think mnewton is
needed here.) I think you want something like
find_root (eq2 - eq1, n, a, b);
where a and b can be determined by inspecting a plot, e.g.
plot2d (rhs (eq2 - eq1), [n, 1, 10]);
or
plot2d (rhs (eq2 - eq1), [n, 1, 100]);
Unfortunately Maxima is not very strong at solving equations
containing logs by symbolic methods. But maybe a numerical
solution is enough here.
HTH
Robert Dodier