E = 1 2 ( ∇ ∇ X u + ( ∇ ∇ X u ) T + ( ∇ ∇ X u ) T ∇ ∇ X u ) ≈ ≈ 1 2 ( ∇ ∇ X u + ( ∇ ∇ X u ) T ) or E K L = 1 2 ( ∂ ∂ U K ∂ ∂ X L + ∂ ∂ U L ∂ ∂ X K + ∂ ∂ U M ∂ ∂ X K ∂ ∂ U M ∂ ∂ X L ) ≈ ≈ 1 2 ( ∂ ∂ U K ∂ ∂ X L + ∂ ∂ U L ∂ ∂ X K ) and e = 1 2 ( ∇ ∇ x u + ( ∇ ∇ x u ) T − − ∇ ∇ x u ( ∇ ∇ x u ) T ) ≈ ≈ 1 2 ( ∇ ∇ x u + ( ∇ ∇ x u ) T ) or e r s = 1 2 ( ∂ ∂ u r ∂ ∂ x s + ∂ ∂ u s ∂ ∂ x r − − ∂ ∂ u k ∂ ∂ x r ∂ ∂ u k ∂ ∂ x s ) ≈ ≈ 1 2 ( ∂ ∂ u r ∂ ∂ x s + ∂ ∂ u s ∂ ∂ x r )