Hi! I’m working on implementing a solver for a non linear elasticity problem, I’ve successfully done so using a newton solver and the Variation() function. I want to try a new setting of the problem en for that I calculated the variation of my energy term by hand, the nonlinear term in this energy has a Determinant and that implies that my new term has a Det(F)F^{-T}, where F is Id(3)+ Grad(u) the usual deformation gradient. I’m having trouble implementing the inverse transposed in my bilinear form. Is there a way to do it? or is something conceptually wrong on what im doing?

Thanks!