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HOW TO FIND THE TANGENT LINE TO A CURVE WITH TI89 CALCULATOR

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 Tangent Line Press F5
  Press ALPHA, then = key (for Tangent)
  Type in value for x or trace function until you reach the value for x
Note: In this case, we are finding tangent line to curve at x = 3.
Note: For parametric equations, type in value for t or trace function until you reach the value for t.
  Press ENTER
Note: In this case, the equation of the tangent line to curve at x = 3 is y = –6x + 14.