# Product Rule

- Author:
- Richard Trimble

## Product rule

The area is formed by the product of two sides u and v.
Both are functions of t (possibly time).
How is the rate of change of u and v linked to that of the product uv?
Consider:
- which sides are changing?
- imagine a small change du in u and dv in v (say 0.1 but could be smaller).
- what would the area of the strip be?
- can you come up with a rule for the rate of change of uv with respect to t?