(4%)(e)在運算 Divergence ∇•A或Cur∇✖A時(A為一向量場),我们選的體積或面積在大少和形狀各有何限制?

(a) At any point (x0, y0, z0) in the domain of a scalar function V(x, y, z), we take a path ae along V= c, where c is a constant, or take a path an along ∇V. Tell me about the main characteristic(主要特徴) of these two paths a: and an, and also what is, the dot product of at and an?