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Tangent/Normal with derivative

  1. Oct 16, 2011 #1
    1. The problem statement, all variables and given/known data
    Find the lines that are (a) tangent and (b) normal to the curve y=x3 at the point (1,1).


    2. Relevant equations



    3. The attempt at a solution
    So first I found the derivative, 3x2. Then I used x=1 to find the slope which is 3.

    (a)y-1=3(x-1)
    y=3x-2

    (b)y-1=(-1/3)(x-1)
    y=(-1/3)x+(4/3)


    Not really sure if I found the slope correctly tho..
     
  2. jcsd
  3. Oct 16, 2011 #2

    SammyS

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    It looks good to me.

    If two lines are perpendicular, then the product of their slopes is -1 .
     
  4. Oct 16, 2011 #3
    Looks good to me. I see no problem with a or b.
     
  5. Oct 16, 2011 #4
    Thanks :p
     
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