Chain Rule

A formula for the derivative of one function, say \(f(y)\), applied to the result of another, say \(g(x)\)
\[ \frac{\mathrm{d}f(g)}{\mathrm{d}x} \Bigg|_x = \frac{\mathrm{d}f}{\mathrm{d}y} \Bigg|_{g(x)} \times \frac{\mathrm{d}g}{\mathrm{d}x} \Bigg|_x \]