Why does the chain rule work?

1 Answer
KillerBunny
Nov 15, 2015

The chain rule is used to differentiate composite function, which are something of the form #f(g(x))#. The rule states that the derivative of such a function is the derivative of the outer function, evaluated in the inner function, times the derivative of the inner function. In formulas:

#d/dx (f(g(x)) = f'(g(x)) * g'(x)#.

You can iterate this procedure with multiple functions, so

#d/dx (f(g(h(x))) = f'(g(h(x))) * g'(h(x)) * h'(x)#, and so on

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