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How to graph the tangent to a curve at some point?

  1. Jan 12, 2010 #1
    Using a graphing software, I'm trying to graph three things:

    1. The function [tex]x^2[/tex].
    2. It's derivative [tex]2x[/tex].
    3. The tangent to the curve at point 3.

    Now I know that that if I want to find the slope of the curve at point 3, I should substitute 3 into the derivative [tex]2x[/tex], which will give 6. What I want is the tangent line, not it's slope, at point 3. What equation should I input into the software to show the tangent to the curve at point 3? Please help.
     
  2. jcsd
  3. Jan 12, 2010 #2
    Asking the program to get the line tangent to a point on the graph probably depends on the program.
    Why not use the equation for a tangent line at point (a, f(a))
    y = f'(a)(x - a) + f(a)
     
  4. Jan 12, 2010 #3
    It worked! How did you derive this equation?

    EDIT: Never mind, I've find out.
     
    Last edited: Jan 12, 2010
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