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Line passing through an Ellipse and a Point

  1. Nov 23, 2009 #1
    Please Help! Line passing through an Ellipse and a Point

    1. The problem statement, all variables and given/known data

    Hi guys, I'm new to the forum and I could really use some help with this problem.

    There is an ellipse with the equation: (X^2/4) + Y^2 = 1

    There is a point on the graph (4,0)

    Find an equation that passes through the line and the point...(must use the chain rule)


    2. Relevant equations

    (X^2/4) + Y^2 = 1

    3. The attempt at a solution

    I attempted to derive the slope of the circle: (DY/DX) = (-.5X)/(2Y)...
    What do I do from here? Was that part even right? Thanks!
     
    Last edited: Nov 23, 2009
  2. jcsd
  3. Nov 23, 2009 #2
    Re: Please Help! Line passing through an Ellipse and a Point

    The line y=0 passes through the point and the ellipse. I think you want a line that passes through the point (4,0) and is tangent to the ellipse, right? In which case there are two of them.
     
  4. Nov 23, 2009 #3
    Re: Please Help! Line passing through an Ellipse and a Point

    Yes, I suppose you could find either equation but the one in the picture shows the line with a negative slope...
     
  5. Nov 23, 2009 #4
    Re: Please Help! Line passing through an Ellipse and a Point

    You need two equations for slope, or dy/dx. One is the slope of the upper half of an ellipse. The other is for a line that passes through the point (4,0).
     
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