Sigma Notation (DP IB Applications & Interpretation (AI)): Revision Note

Sigma Notation

What is sigma notation?

• Sigma notation shows the sum of a certain number of terms in a sequence

• The symbol Σ is the capital Greek letter 'sigma' and stands for 'sum'

• e.g. for

  • The formula after the Σ tells you how to work out each term

    • It is the n^th term formula but written in instead

  • The lower limit tells you which term to start on

  • The upper limit tells you which term to end on

  • So

• The letter can also be used (instead of )

• Be careful, as not all lower limits start at 1

  • For example   or