Hi,
consider this:
(%i1) solve( exp(-t/5017500) = 1/2, t);
(%o1) [t = 5017500 log(2)]
there is really an infinite number of complex solutions, but luckily
solve only found the real solution which is what I was interested in,
since t represents the time it will take for a capacitor to discharge to
50%.
If instead of measuring time in microseconds, which is what I used
above, we used milliseconds, the solutions shown, include one of the
complex solutions:
(%i4) solve( exp(-10*t/50175) = 1/2);
(%o4) [t = 10035*log(-sqrt(2)),t = 10035*log(2)/2]
my students have a tendency to always work with seconds:
(%i5) solve( exp(-10000*t/50175) = 1/2);
which leads to 400 solutions and Wxmaxima even refuses to show them.
to_poly_solve gives the solution in a nicer way
%union([t = (4014*%i*%pi*%z6+2007*log(2))/400])
Is there a way to restrict solve or to_poly_solve to only real solutions?
Regards,
Jaime