Numerical Derivative

WARNING: The numerical derivative function on the calculator may give an incorrect answer if you are trying to do a computation at a sharp point, cusp, or any other interesting feature on a function.

Suppose we want to use the calculator to compute the slope of the tangent line for the function at x=4.

Press and enter the function into Y₁.

Make sure the function is turned on.

Method 1: Using the command nDerive

The syntax for this command is: nDerive(function,X,value)

From the home screen do the following.

• Press
• Choose 8:nDeriv.
• Now enter the variable name that corresponds to where the formula was entered, for example Y₁
  • Note: You may choose to just type the function at this point.
• Press
• Type the value of X.
• Press
• Press

Using the example from above should now display the following.

If needed you can convert the answer to a fraction.

Method 2: Using a Graphing Screen

• Press and enter the function into Y₁.
• Set the window. Be sure that the x-value, you want to compute the derivative for, is between the X-min and X-max values. For this problem I used
  X-min = -10, X-max = 10, Y-min = -10, and Y-Max = 60
  
  • Note: The y-scale is not important. The Zoom Fit option may be used for these values.

• Press
• Press
• Choose 6:dy/dx.
• Enter the value of x where you want to compute slope of the tangent line. For the above example this is 4. The calculator should now display the following.

• Press

The calculator should now display the following.

It is not possible to convert the answer from this method to a fraction.