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How to add up a series with sigma on a TI-89 Titanium

By E-Code · updated

Press F3 (Calc) and 4 for Σ(, type the term, the counting letter, the first and last values, close with ) and press ENTER: Σ(1/n,n,1,5) gives exactly 137/60.

Step by step

  1. Pick Σ(. F3 4 Press F3 for Calc, then 4 for Σ(, the sum.
  2. Type 1/n, n, 1, 5. 1 ÷ ALPHA 6 , ALPHA 6 , 1 , 5 ) Type 1/n, then n, 1, 5 and ). ALPHA 6 types n. That is: the term, the letter that counts, then where it starts and stops.
  3. Add it up. ENTER Press ENTER. The TI-89 adds 1 + 1/2 + 1/3 + 1/4 + 1/5 as fractions.
  4. Read the sum. 137/60, exactly. ◆ ENTER gives the decimal, 2.28333.

What the screen shows

137/60, exactly. ◆ ENTER gives the decimal, 2.28333.

Look for 137/60 on the screen.

Try it with the keys lit up

This guide is one of E-Code's Learn lessons. Open it on E-Code's TI-89 calculator and each key lights up in turn as you press it.

Try “Add up a series with sigma” on the TI-89 calculator

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