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How to find a derivative at a point on a TI-89 Titanium

By E-Code · updated

Press 2nd 8 for d(, type the function, a comma, the variable and ), then ENTER: d(x^3,x) gives 3·x^2. Press ▶ to keep the line, add |x=2 (| is the with key) and press ENTER for the value at that point, 12.

Step by step

  1. Type d(. 2nd 8 Press 2nd, then 8. 2nd 8 is d, the derivative. It is not the letter d: that one won't differentiate.
  2. Type the function. X ^ 3 , X ) Type x^3, a comma, x and ). The x after the comma says which letter to differentiate by.
  3. Differentiate it. ENTER Press ENTER.
  4. Keep the line. ▶ Press ▶. The last entry stays on the line, highlighted; ▶ puts the cursor at its end so you can add to it.
  5. Add |x=2. | X = 2 Type | (the with key) and x=2. It means: work this out with x = 2.
  6. Get the slope at x = 2. ENTER Press ENTER.
  7. Read both answers. The derivative of x³ is 3x², and at x = 2 it is 12: the slope of the curve there.

What the screen shows

The derivative of x³ is 3x², and at x = 2 it is 12: the slope of the curve there.

Look for |x=2 12 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 “Find a derivative at a point” on the TI-89 calculator

Related

Math programs for the TI-89 Titanium:

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