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To differentiate composite functions of the form f(g(x)) we use the chain rule (or "function of a function" rule). The derivative of the function of a function f(g(x)) can be expressed as: f'(g(x)).g'(x)
Alternatively if y=f(u) and u = g(x) then \displaystyle \frac{dy}{dx} = \frac{dy}{du} \times \frac{du}{dx}

## Summary/Background

The chain rule is also known as the "function of a function" rule. It can be stated in a number of ways.
If y = f(u), u = g(x) then \displaystyle\frac{dy}{dx} = \frac{dy}{du}\times \frac{du}{dx}
Here are some more examples:
\displaystyle \frac{d((x+1)^6)}{dx} = 6(x+1)^5.1 = 6(x+1)^5
\displaystyle \frac{d(e^{10x})}{dx} = e^{10x}.10 = 10e^{10x}
\displaystyle \frac{d( \ln x^2)}{dx} = \frac{1}{x^2}.2x = \frac{2}{x}

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## Glossary

### chain rule

A rule for differentiating a function of a function:
dy/dx = dy/du x du/dx.

### composite

made of a combination of simpler shapes or bodies

### derivative

rate of change, dy/dx, f'(x), , Dx.

### differentiate

to find the derivative of a function

### function

A rule that connects one value in one set with one and only one value in another set.

### rule

A method for connecting one value with another.

### union

The union of two sets A and B is the set containing all the elements of A and B.

Full Glossary List