The Marksmith AU

The inside derivative you forgot

You differentiate the outer function and stop.

$\frac{d}{dx}f(g(x)) = f'(g(x))\,g'(x)$ — the inner derivative always multiplies. Integration is the same rule read backwards: recognise $g'(x)\,f'(g(x))$ as an exact derivative.

Next time: After differentiating a composite, ask what the inside derivative was.

Try it: Work one on a block