Grade 12 · Theory
Sigma notation and series
Sequences and series · about 3 min
Visual overview: Sigma notation and series1 MIN READ
2 study sections · pause after each one and recall the key ideaSigma notation is compact shorthand for a sum, and reading it correctly is half the battle.
Key points- The number below Σ is the starting value of the counter; the number above is where it stops.
- Substitute the first few values to see the pattern and identify a, d or r.
- The number of terms = (top − bottom) + 1.
- Choose the arithmetic or geometric sum formula once you know the type.
- Sigma (Σ) — notation meaning "the sum of".
EXAM TIP
always expand the first two or three terms — it instantly reveals a, and whether the series is arithmetic or geometric.