AQA A Level Maths: Pure复习笔记4.5.2 Sigma Notation

Sigma Notation

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!

What do I need to be able to do with sigma notation?

  • Sigma notation can be used to represent both arithmetic series and geometric series
    • Writing out the first few terms will help you


  • To work out such a sum use the arithmetic and geometric series formulae
  • As long as the expressions being summed are the same you can add and subtract in sigma notation
    • For example:

Exam Tip

Be careful when more than one letter appears in a sigma notation question. 4.3.2-Sigma-Not-Illustr-5

Worked Example