To find out more about them, let us scalarmultiply each side of Eq. (3) by an arbitrary unit vector nj", and take into account the evident orthonormality condition: \[\mathbf{n}_{j^{\...To find out more about them, let us scalarmultiply each side of Eq. (3) by an arbitrary unit vector nj", and take into account the evident orthonormality condition: nj′⋅nj′′=δjj′′, where δjj′ is the Kronecker delta symbol. 2 As a result, we get dnj⋅nj′′=dφij′′ Now let us use Eq. (5) to calculate the…