请问为什么求偏导时符号不一样？

偏导数符号∂ 是全导数符号d 的变体，这个符号是阿德里安-马里·勒让德引入的，并在雅可比的重新引入后得到普遍接受。The symbol used to denote partial derivatives is ∂. One of the first known uses of this symbol in mathematics is by Marquis de Condorcet from 1770, who ...