i have 12 second order non linear coupled partial differential equations (Euler-Lagrange Equations) in 12 variables {u1a(x1+l/2),u2a(x1+l/2),u3a(x1+l/2),theta1a(x1+l/2),theta2a(x1+l/2),theta3a(x1+l/2), u1p(x1,x2),u2p(x1,x2),u3p(x1,x2),theta1p(x1,x2),theta2p,theta3p}

also there are 17 lagrange multipliers in these equations which are also to be solved, using 17 constraints equations.

along with 48 boundary conditions. These have emerged out of variational formulations

How should I save my result-expression so as to be able to use it directly in other file without having to generate it again.

please help
regards,

Hi!

I am a mechanical engineer.

I want to differentiate a potential energy functional (a multivariable functional combination of integrals) in the variational calculus to get the Euler-Lagrange equations and boundary conditions and then to solve ODE's and PDE's to get a closed form solution.

The form of PE:=F(x1,x2,x3,w1(x1,x2,x3),w2(x1,x2,x3),w3(x1,x2,x3),diff(w1,x1),etc...)

Interested in getting diff(F,w1)  and diff(F,diff(w1,x1)).