You perfectly answer to my question. Great!
However, how do you find this code ? Indeed, i haven't see this code anywhere in the help section.
Thank you for your help.

You perfectly answer to my question. Great!
However, how do you find this code ? Indeed, i haven't see this code anywhere in the help section.
Thank you for your help.

Here the detail of the equation eq1pp

eq1pp := R(t) = -(-sin(theta[0]+phi)*Isup-sin(theta[0]+phi)*L[fixe]^2*M[fixe]-sin(theta[0]+phi)*L[r]^2*M[r]-sin(theta[0]+phi)*L[sup]^2*M[sup]+cos(theta[0]+phi)*a*sin(phi)*L[fixe]*M[fixe]+cos(theta[0]+phi)*a*sin(phi)*L[r]*M[r]+cos(theta[0]+phi)*a*sin(phi)*L[sup]*M[sup])*(diff(theta(t), t, t))/(a*sin(phi))+Ctheta*sin(theta[0]+phi)*(diff(theta(t), t))/(a*sin(phi))+Ktheta*theta(t)*sin(theta[0]+phi)/(a*sin(phi));

Thank you for you help