Solving Equations With logs



On 2/18/08, Marco Carmosino <mogunus at gmail.com> wrote:

> Thanks very much, numeric solutions are fine and find_root works great for
> two equations. However, I'm having trouble solving where I just want to set
> my equation equal to a constant:
>
> (%i50) find_root(log2(n)=10^6, n, 0, 10^60);
>                                       log(n)
> (%o50)           find_root(------ = 1000000, n, 0.0, 1.0E+60)
>                                       log(2)

I see a couple of problems here. find_root wants to evaluate
the equation at the endpoints, but log(0.0) isn't a number.
Also, the solution to this equation is very, very much greater
than 10^60. Perhaps the equation has been misstated ??

> (%i52) solve(log2(n)=10^6,n);
>
> This produces a very, very long string of numbers.

Well, log2(n) = 10^6 => n = 2^(10^6) which is a number of
several hundred thousand digits, if I'm not mistaken ....

best

Robert Dodier