Hello eveyone,

I'm experiencing a frustrating problem, trying to get maple to solve a system of differential equations. I have defined my system as:

f:=1-2*(n+1)*b*xi^2*nu(xi):

sys:={diff(nu(xi),xi)=(theta(xi)^n - 3*nu(xi)), diff(psi(xi),xi)=(n+1)*b*xi*theta(xi)^n*(1+b*theta(xi))/f, diff(theta(xi),xi)=-(nu(xi)+b*theta(xi)^(n+1))*xi*(1+b*theta(xi))/f, theta(xi=0)=1, nu(xi=0)=1/3};
 

The only part worth concentrating on is the part I've made bold. I then can solve the system near xi=0 witha  series solution:

dsolve(sys,{nu(xi),theta(xi),psi(xi)}, type='series'): simplify(%);

When I do this, everything works fine. However if I modify the bold equation slightly by dividing the right hand side by xi, like this:

sys:={diff(nu(xi),xi)=(theta(xi)^n - 3*nu(xi))/xi, diff(psi(xi),xi)=(n+1)*b*xi*theta(xi)^n*(1+b*theta(xi))/f, diff(theta(xi),xi)=-(nu(xi)+b*theta(xi)^(n+1))*xi*(1+b*theta(xi))/f, theta(xi=0)=1, nu(xi=0)=1/3};

And then I try to solve, dsolve returns nothing at all. I just press enter, nothing happens and the cursor goes to the next line. Does maple not like when I explicitly divide the RHS by the dependant variable, which starts at zero? I have tried the following variations in place of the bold text above (which I realize are the exact same thing) to try to get it to recognize the equation, but with no luck.

xi*diff(nu(xi),xi)=(theta(xi)^n - 3*nu(xi))

0= -xi*diff(nu(xi),xi) + (theta(xi)^n - 3*nu(xi))

Any ideas? I appreciate it!

Taylor