10. Calculus identities#
Here some calculus identities are listed and proved, often using Cartesian coordinates and index notation. While these identities are independent on the choice of the coordinates - as calculus is - a generic set of coordinates can be used to prove them, and Cartesian coordinates are the most convenint choice.
(10.1)#
Proof.
Uusing the identity
and index notation for Cartesian coordinates,