Evaluate sigma (Σ) notation, list the terms of a sequence, or total a series without adding by hand.
In short: Listing a sequence generates its terms from a formula or rule, and summing a series adds a chosen number of terms. On a GDC you can build the terms in a list, use a sequence or sum function, and read the total. Use it to check arithmetic and geometric sequence answers and partial sums.
| TI-84 Plus CE | Casio fx-CG50 and fx-CG100 | TI-Nspire CX | |
|---|---|---|---|
| Key sequence | List terms with 2nd → STAT (LIST) → OPS → 5:seq(expr, n, start, end); total with 2nd → STAT → MATH → 5:sum(seq(...)). | OPTN → LIST → Seq( builds the list; OPTN → LIST → Sum totals it. | Type seq(expr, n, start, end) to list and sum(seq(...)) to total, or use the Σ template from the maths templates. |
Tip: Many calculators have a Σ( template - enter the term, the variable, and the two limits directly.
Tip: Many calculators have a Σ( template - enter the term, the variable, and the two limits directly.
Tip: Many calculators have a Σ( template - enter the term, the variable, and the two limits directly.
Here's a real IB-style question that uses exactly this technique.
Find the value of ∑ₙ₌₁¹⁰ (2n + 1).
Evaluate sigma (Σ) notation, list the terms of a sequence, or total a series without adding by hand. Evaluating a sum written in sigma (Σ) notation without expanding every term by hand. Listing the terms of a sequence to spot a pattern before finding a formula.
1. Write the general term, e.g. uₙ = 3n − 1, and the range of n. 2. List terms with 2nd → STAT (LIST) → OPS → 5:seq(expr, n, start, end); total with 2nd → STAT → MATH → 5:sum(seq(...)). 3. For Σ notation the lower and upper limits are the start and end values of n.
1. Write the general term, e.g. uₙ = 3n − 1, and the range of n. 2. OPTN → LIST → Seq( builds the list; OPTN → LIST → Sum totals it. 3. For Σ notation the lower and upper limits are the start and end values of n.
1. Write the general term, e.g. uₙ = 3n − 1, and the range of n. 2. Type seq(expr, n, start, end) to list and sum(seq(...)) to total, or use the Σ template from the maths templates. 3. For Σ notation the lower and upper limits are the start and end values of n.
Many calculators have a Σ( template - enter the term, the variable, and the two limits directly.
In the worked example on this page (2 marks, Paper 2), the marks are: M1: Use the sum function with lower limit 1, upper limit 10; A1: 120.
Questions that need this technique link back to this guide. Try one in practice mode, or see every GDC guide.