Derivative of Composite Function/Corollary

Theorem
Let $f, g, h$ be continuous real functions such that:
 * $y = f \left({u}\right), x = g \left({u}\right)$

Then:
 * $\displaystyle \frac {\mathrm d y}{\mathrm d x} = \frac {\left({\dfrac {\mathrm d y}{\mathrm d u} }\right)}{\left({\dfrac {\mathrm d x}{\mathrm d u} }\right) }$

for $\dfrac {\mathrm d x}{\mathrm d u} \ne 0$.