# The Trapezium Rule

The trapezium rule is a way of estimating the area under a curve. We know that the area under a curve is given by integration, so the trapezium rule gives a method of estimating integrals. This is useful when we come across integrals that we don't know how to evaluate.

The trapezium rule works by splitting the area under a curve into a number of trapeziums, which we know the area of.

If we want to find the area under a curve between the points x_{0} and x_{n}, we divide this interval up into smaller intervals, each of which has length h (see diagram above).

Then we find that:

where y_{0} = f(x_{0}) and y_{1} = f(x_{1}) etc

If the original interval was split up into n smaller intervals, then h is given by: h = (x_{n} - x_{0})/n

**Example**

You may be also be asked in your exam to summarise an advantage and a limitation of the trapezium rule.

**An Advantage:** The trapezium rule is relatively simple to apply and understand compared to some other numerical integration methods.

**A Limitation:** The trapezium rule may not provide accurate results for functions with rapidly changing slopes or high curvature, requiring more intervals to achieve accuracy, which can increase computational complexity.