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How to use variables as integral limits on a TI-84 Plus CE

By E-Code · updated

Store the limits first (0 STO→ ALPHA A, 2 STO→ ALPHA B), then press MATH 9 for the ∫ template and fill it with A ▶ B ▶ X² ▶ X, then ▶ and ENTER: 2.666…. Store new limits and run the same line again with 2nd ENTRY.

Step by step

  1. Lower bound in A. 0 STO→ ALPHA MATH Type 0, press STO→, then ALPHA and MATH for A: A holds the lower bound.
  2. Store it. ENTER Press ENTER.
  3. Upper bound in B. 2 STO→ ALPHA APPS ENTER Type 2, STO→, ALPHA and APPS for B, then ENTER: B holds the upper bound.
  4. Open MATH. MATH Press MATH. Item 9 is fnInt(, the definite integral.
  5. Pick fnInt(. 9 Press 9. The ∫ template appears, with the cursor in the lower limit box.
  6. The bounds as letters. ALPHA MATH ▶ ALPHA APPS ▶ Type ALPHA MATH for A, press ▶, type ALPHA APPS for B, and press ▶ into the brackets.
  7. Function and variable. X,T,θ,n X² ▶ X,T,θ,n ▶ Type X,T,θ,n x² for X², press ▶, then X,T,θ,n for dX and ▶ to leave the template.
  8. Work it out. ENTER Press ENTER.
  9. Change the bounds. 2.666… is the integral of X² from A = 0 to B = 2. Store new values in A and B, then press 2nd ENTRY until the ∫ line is back, and ENTER: no retyping.

What the screen shows

2.666… is the integral of X² from A = 0 to B = 2. Store new values in A and B, then press 2nd ENTRY until the ∫ line is back, and ENTER: no retyping.

Look for 2.666666667 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-84 calculator and each key lights up in turn as you press it.

Try “Use variables as integral limits” on the TI-84 calculator

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