In calculus [Calculus], the chain rule is a formula that expresses the derivative [Derivative (math)] of the composition of two differentiable functions \(f\) and \(g\) in terms of the derivatives of \(f\) and \(g\). More precisely, if \(h=f\circ g\) is the function such that \(h(x)=f(g(x))\) for every \(x\), then the chain rule is, in Lagrange’s notation [Lagrange’s notation],
\(h’(x)=f’(g(x))g’(x)\).
or, equivalently,
\(h’=(f\circ g)’=(f’\circ g)\cdot g’\).