If we define I 0 := 1 and I 4 := 0 , we can write the above as [ ∂ ∂ I 1 ∂ ∂ A λ λ 3 + ∂ ∂ I 2 ∂ ∂ A λ λ 2 + ∂ ∂ I 3 ∂ ∂ A λ λ + ∂ ∂ I 4 ∂ ∂ A ] 1 + A T ⋅ ⋅ ∂ ∂ I 0 ∂ ∂ A λ λ 3 + A T ⋅ ⋅ ∂ ∂ I 1 ∂ ∂ A λ λ 2 + A T ⋅ ⋅ ∂ ∂ I 2 ∂ ∂ A λ λ + A T ⋅ ⋅ ∂ ∂ I 3 ∂ ∂ A = [ I 0 λ λ 3 + I 1 λ λ 2 + I 2 λ λ + I 3 ] 1 .