# AQA A Level Maths: Pure复习笔记7.3.3 Chain Rule

### Chain Rule

#### What is the chain rule?

• The chain rule is a formula that allows you to differentiate composite functions
• If y is a function of u, and u is a function of x, then the chain rule tells us that: This allows us to differentiate more complicated expressions:

#### What are the special cases of the chain rule?

• Exam Tip
• The chain rule formulae are not in the exam formulae booklet – you have to know them.
• When using the chain rule be sure to keep your functions straight (ie which function is y and which is u, or which is f and which is g).