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Error: Unable to find symbolic solution

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Sabrina Garland
Sabrina Garland on 24 Oct 2021
Commented: Sabrina Garland on 24 Oct 2021
syms y(x)
ode= diff(y, x)== (-(5*y)/(2*x))/(1- ((1/(2*x))^2)*((y/(1-y))^(3/5)));
cond = y(1/2)==1/2;
ySol(x) = dsolve(ode, cond)
Warning: Unable to find symbolic solution
> In dsolve (line 209) ySol(x) = [ empty sym ]
What am I doing wrong? Please Help
  2 Comments
John D'Errico
John D'Errico on 24 Oct 2021
Edited: John D'Errico on 24 Oct 2021
  1. Just because you want it to happen, symbolic solutions need not always exist for all problems. In fact, it is a vanishingly small number of problems with symbolic solutions.
  2. You can always use a numerical solver, perhaps ODE45 might be a good place to start. It will probably fail, because at y(1/2) == 1/2, there is a derivative singularity.
  3. Finally, sometimes a solution can be found by a clever transformation of the problem. This is why they pay the mathematicians the big bucks. (Yeah, right. Like that often happens.) Ok, the good mathematicians.
  4. The derivative singularity at y(1/2) == 1/2 may suggest a good transformation may exist, but you would need to be creative.
Ok, do you want something a bit more useful? If I had to guess, no explicit solution probably exists. The result is going to exist, if at all, as an implicit function.

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