Alissa Eichinger

Edlf 345

Let’s say we need to find the derivative of a function at a point. First, you need to graph your function.

  1. Press the y = button.
  2. Type in the equation
  3. Press the graph button. (You may need to adjust your window like we discussed in class last time through the zoom key or through changing the window specifications.)
  4. Press the 2nd button then the trace button, then press 6 for dy/dx.
  5. Then you will be back to the graph screen, and now you want to type in the value for which you want the derivative. (the x-value)
  6. Then it will tell you at the bottom of the screen dy/dx = something. And there’s your derivative.

Ex. You want to find the derivative of y = x2 at x = 2. Answer: dy/dx = 4.

Along the same lines, now let’s say you have a function and you’d like to graph the derivative of that function without having to determine the actual derivative. (

  1. Go to the y = button again. (I’m assuming you’ve already typed in the function on one of the lines of the y = screen. Like if you were proceeding directly from doing the previous activity. If you haven’t, type in your function now.) Arrow down to the next empty line.
  2. Press the math button.
  3. Press 8 for nDerive (
  4. Go to Vars.
  5. Arrow right to Y-Vars
  6. Press enter for Function
  7. Type the number for which line of your y = screen contains the function for which you desire the derivative. (For example, say you typed your function y = x2 on the first y = line, then you are wanting the derivative of the function on line Y1. So if you were on the second line, you choose Y2, and so on.)
  8. Then now that you are back at your y = screen, type a comma (with the comma button), then type an X (with your X button), and then a comma and then another X and then a closed parenthesis. So you line should look like: Y2 = nDerive(Y1, X, X) (I’m afraid I don’t remember exactly what the two Xs are necessary for. I believe one stands for the variable in which you are working, and the other is possibly there to specify the domain, like over all X)
  9. Then you are ready to press graph.
  10. Now unless you’ve unchosen your original function, it will graph both functions. Which is good if you’d like to look at the two and show the relationship between a function and it’s derivative. However, if you’d like the original not to be graphed, you need to go back to the y = screen.
  11. Arrow up/down to the function you do not wish to be graphed. Arrow left/right so that your cursor is over top of the equal sign.
  12. Press enter. When you arrow off of the = sign, it shouldn’t be highlighted.
  13. Now when you press graph, it should only graph your desired derivative.

Ex. You started with your original function y = x2 on line Y1 of your y = screen. You want to graph the derivative of this function without having to know that dy/dx of x2 is 2x. So you are utilizing the nDerive function of your calculator. In essence, you are telling the calculator, I want you to graph the derivative of the function I typed into Y1, in the variable X over all of X. And then by following the above steps, the calculator does, and you have your derivative. This may not seem that wonderful since you know dy/dx of x2 is 2x, however, you may want to illustrate the relationships that exist between a function and its derivative using a not so well known function, i.e., one in which you may not know the derivative off the top of your head. And with the nDerive function of the calculator, you can do that. 