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HOW TO FIND NUMERICAL DERIVATIVES WITH TI89 CALCULATOR

Method 1: Using d() function on Home screen
Steps Key Sequence Screens
1. Set Up Differentiator Press F3, then ALPHA key, then = key (for nDeriv()
2. Type the Function  
3. Input Variable Press comma, then the variable
4. Input Value for h Press comma, then 0.01 (or smaller)
NOTE: The default value for h is 0.001
4. Execute Derivative Press ')', then ENTER
 
Method 2: Using graph of function
Steps Key Sequence Screens
1. Input Function, Piecewise-Defined Function, or Parametric Equation. Press DIAMOND key, then F1 key (for Y=)
  Type the function
2. Graph Press DIAMOND key, then F3 key
3. Find Derivative Press F5
  Press 6 (for Derivatives)
  Select appropriate derivative
  Type in value for x or trace function until you reach the value for x.
Note: For a parametric equation: type in value for t or trace curve until you reach the value for t.
Note: In this case, we are finding the derivative of the function at x = 1.
  Press ENTER
Note: In this case, the derivative of the function at x = 1 is dy/dx = –1.