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Homework Help: Polar graphs really important and tangents!

  1. Jun 20, 2013 #1
    Hi, I really need help with this as exam is tomorrow

    The question is to find the points on the cardioid r=a(1+costheta) where the tangents are perpendicular to the initial line

    here is the answer


    Why is pi not included in the solution, while if I was finding parallel to the initial line then pi would be included.

    please help
  2. jcsd
  3. Jun 20, 2013 #2


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    Science Advisor
    Homework Helper

    hi phospho! :smile:
    you're solving dx/dθ = 0

    but you're using an x,y graph, so you really need to solve dx/dy = 0

    ie dx/dθ / dy/dθ = 0

    the solutions to this are the same as the solutions to dx/dθ = 0, except if dy/dθ = 0 (which it is for θ = π) :wink:
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