$\frac{\partial x}{\partial y} \cdot \frac{\partial y}{\partial z} \cdot \frac{\partial z}{\partial x} = -1$ according to the triple product rule
However, it would be 1, if derivatives behaved like fractions.
And in Nonstandard Calculus derivatives do behave like fractions. (it treats derivatives as fractions of actual infinitesimal quantities, rather than d/dx applied to a function)
So, how does Nonstandard Calculus get the correct answer here?
(which it must since it is equivalent to standard calculus)