Could you do this?
E₁₁, E₂₂ = Symbolics.solve_for( [E₁ ~ 0, E₂ ~ 0], [d(d(x)), d(d(y))] )
That should work in the mixed case.
Could you do this?
E₁₁, E₂₂ = Symbolics.solve_for( [E₁ ~ 0, E₂ ~ 0], [d(d(x)), d(d(y))] )
That should work in the mixed case.