27. Differentiation of Scalar Function Scalar Function $ \phi =\phi (s) $ in the $ x_{i},x_{i}' $ coordinates, $ \phi =\phi ', s=s' \Rightarrow d\phi =d\phi ', ds=ds' $ $ \frac{d\phi }{ds}=\frac{d\phi '}{ds'}=(\frac{d\phi }{ds})' $ 28. Differentiationn of Vector Function Vector Function $ \vec{A} $ w.r.t. a scalar S $ A_{i}'=\sum_{j}^{}\lambda _{ij}A_{j} $ $ \frac{dA_{i}'}{ds'}=\frac{d}{ds'}\sum..