Graph the Derivative of a Function on the TI-84 Plus

By Jeff McCalla, C. C. Edwards

In calculus, you need to graph the derivative of a function in order to find its critical points, which you can do on your TI-84 Plus calculator. Just follow these steps:

  1. Enter your functions in the Y= editor.

  2. Use the arrow keys to place your cursor in an open equation in the Y= editor.

  3. Press [MATH][8] to access the nDeriv template.

  4. Press

    image0.jpg

    then press [ALPHA][TRACE] and choose your function, then press the right arrow and

    image1.jpg

    See the first screen. This is a sneaky move. You aren’t using the nDeriv( template to take the derivative at a specific x-value. Instead, by taking the derivative at x = x, you are taking the derivative at all points where the function is defined.

    image2.jpg

  5. Press [GRAPH] to display the graph of your function and the derivative of the function.

    See the second screen.

  6. Press [2nd][TRACE] to access the Calculate menu.

  7. Press [2] to select the zero option.

  8. If necessary, repeatedly press the up- and down-arrow keys until the derivative function appears in the border at the top of the screen.

    Don’t forget to do this step!

  9. Enter the Lower and Upper Bounds, then a guess and press e.

    This is illustrated in the third screen.