d f = ∂ ∂ f ∂ ∂ t d t + ( ∂ ∂ f ∂ ∂ x d x + ∂ ∂ f ∂ ∂ y d y + ∂ ∂ f ∂ ∂ z d z ) + ( ∂ ∂ f ∂ ∂ p x d p x + ∂ ∂ f ∂ ∂ p y d p y + ∂ ∂ f ∂ ∂ p z d p z ) = ∂ ∂ f ∂ ∂ t d t + ∇ ∇ f ⋅ ⋅ d r + ∂ ∂ f ∂ ∂ p ⋅ ⋅ d p = ∂ ∂ f ∂ ∂ t d t + ∇ ∇ f ⋅ ⋅ p m d t + ∂ ∂ f ∂ ∂ p ⋅ ⋅ F d t