What is sigma notation?
- The symbol Σ is the capital Greek letter sigma – that's why it's called 'sigma notation'!
- 'Σ' stands for 'sum' – the expression to the right of the Σ tells you what is being summed, and the limits above and below tell you which terms you are summing
- Be careful – the limits don't have to start with 1!
- For example: or
What do I need to be able to do with sigma notation?
- Sigma notation can be used to represent both arithmetic progressions and geometric progressions
- Arithmetic will have the form
- Geometric will have the form
- Writing out the first few terms will help you
- To work out such a sum use the formulae for the sum of arithmetic and geometric progressions
- As long as the expressions being summed are the same you can add and subtract in sigma notation
- For example:
Be careful when more than one letter appears in a sigma notation question.