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Differential Equation Problem?

  1. Feb 11, 2008 #1
    1. The problem statement, all variables and given/known data
    In 1692, Johann Bernoulli was teaching the Marquis de l'Hopital calculus in Paris. Solve the following problem, which is similar to the one they did. What is the equation of the curve which has subtangent equal to twice its abscissa.

    2. Relevant equations
    None


    3. The attempt at a solution
    Honestly I'm not really sure where to start. Heck, I'm not even seeing how it's part of the differential equations chapter in my math book. Could anyone just me a push in te right direction?
     
  2. jcsd
  3. Feb 11, 2008 #2

    Dick

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    The subtangent is just f(x)/f'(x), isn't it? What's twice the abscissa? Looks like an ODE to me.
     
  4. Feb 11, 2008 #3
    The subtangent is twice the abscissa (which is like a distance on the x-axis?) so...

    2f(x)/f'(x) = x?
     
  5. Feb 11, 2008 #4

    Dick

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    Looks more to me like f(x)/f'(x)=2x.
     
  6. Feb 11, 2008 #5
    Yeah I just fail at reading XD

    Thanks. But I do have one more question what exactly is a subtangent?
     
    Last edited: Feb 11, 2008
  7. Feb 11, 2008 #6

    Dick

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