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Slope of the tangent line of an intersection - Directional Derivatives

  1. May 9, 2010 #1
    1. The problem statement, all variables and given/known data
    Find the slope of the tangent line to the curve of intersection of the vertical plane x - y + 1 =0 and the surface z = x2+y2 at the point (1, 2, 5)

    2. Relevant equations
    Gradients, Cross products

    3. The attempt at a solution

    I'm pretty lost here. I think I have to cross the two gradients of the functions that I have to find the intersection at (1, 2, 5). However, what then?
  2. jcsd
  3. May 10, 2010 #2


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    Homework Helper

    how about finding the horizontal direction of the plane, then using it to find the directional derivative....
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