混合偏导数f_(yx)(x,y)与f_(xy)(x,y)相等的条件

The Equality Conditions of Mixed Partial Derivatives f_(yx)(x,y) and f_(xy)(x,y)

对二元函数的两个混合偏导数fyx(x,y)及fxy(x,y)进行了进一步研究,并得出了它们相等的一个充分条件,该条件比[1]中给出的条件更弱.

A further research is made on the two mixed partial derivatives of the binary function and comes to a full condition for their equality, which is weaker than the condition given in.