Hi, I'm new to sympy and I'm trying to understand how to use dsolve. (I'm creating an ipython notebook for a class.)
I'm creating my DE like this: de = Eq(u(t).diff(t, t) + 4*u(t), 0) print(de) 4*u(t) + Derivative(u(t), t, t) == 0 soln = dsolve(de, u(t)) print(soln) u(t) == C1*sin(2*t) + C2*cos(2*t) So far now everything is perfect. But if I try to change the number 4 for a "generic" symbol (f**2) I do not get u(t) == C1*sin(f*t) + C2*cos(f*t) as I expected, insted I get a more "comprehensive" solution below. What am I doing wrong? >>> d2udt2 = Eq(u(t).diff(t, t) - f*(-f*u(t)), 0) >>> print(d2udt2) f**2*u(t) + Derivative(u(t), t, t) == 0 u(t) == (C1*sin(t*((-re(f)**2 + im(f)**2)**2 + 4*re(f)**2*im(f)**2)**(1/4)*Abs(sin(atan2(-2*re(f)*im(f), -re(f)**2 + im(f)**2)/2))) + C2*cos(t*((-re(f)**2 + im(f)**2)**2 + 4*re(f)**2*im(f)**2)**(1/4)*sin(atan2(-2*re(f)*im(f), -re(f)**2 + im(f)**2)/2)))*exp(-t*((-re(f)**2 + im(f)**2)**2 + 4*re(f)**2*im(f)**2)**(1/4)*cos(atan2(-2*re(f)*im(f), -re(f)**2 + im(f)**2)/2)) + (C3*sin(t*((-re(f)**2 + im(f)**2)**2 + 4*re(f)**2*im(f)**2)**(1/4)*Abs(sin(atan2(-2*re(f)*im(f), -re(f)**2 + im(f)**2)/2))) + C4*cos(t*((-re(f)**2 + im(f)**2)**2 + 4*re(f)**2*im(f)**2)**(1/4)*sin(atan2(-2*re(f)*im(f), -re(f)**2 + im(f)**2)/2)))*exp(t*((-re(f)**2 + im(f)**2)**2 + 4*re(f)**2*im(f)**2)**(1/4)*cos(atan2(-2*re(f)*im(f), -re(f)**2 + im(f)**2)/2)) Thanks, -Filipe -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/1395f3d9-f6ea-4167-bc0c-3a9b7e1e1e5d%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
