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Minimum distance

  1. Oct 26, 2014 #1
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    1. The problem statement, all variables and given/known data
    Find the minimum distance between the curves y^2 - xy - 2x^2 = 0 and y^2 = x - 2.
    Ans: 7/(4*root2)

    2. Relevant equations


    3. The attempt at a solution
    It's supposed to be done using concepts from parabolas. I tried using calc but it got convoluted.
     
  2. jcsd
  3. Oct 26, 2014 #2

    Dick

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    y^2 - xy - 2x^2 splits into two linear factors. That makes it easier since the graph becomes two lines.
     
  4. Oct 27, 2014 #3
    Ohhh ok. I didn't realise that was a pair of straight lines.
    I did it now. Split it into y=-x and y=2x. Drew a rough graph. It's clear from the graph that y=-x is closer. So, using the slope form of tangent to a parabola, I wrote the equation of tangent with the slope -1, and figured out the distance between the two parallel lines, which comes out to be the answer. Thanks :D
     
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