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Homework Help: Parametric Curves and Tangent line equations

  1. Nov 19, 2005 #1
    Find an equation of the tangent line to the curve with parametric equations x=tsint, y=tcost at the point (0,-π).

    went dy/dt / dx/dt --> cost - tsint/sint + tcost

    t not given so figured it could be:

    x=t(sin(1)) --> t= x/sin(1)


    y=t(cos(1)) --> t= y/cos(1)

    wondering if this is the right way to do it...looks really messy...help would be nice. Thanks.
  2. jcsd
  3. Nov 20, 2005 #2


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    Homework Helper

    You can find t by checking which t is necessary to be get at (0,-pi). If x has to be 0, either t or sint has to be zero. But with t = 0, y is 0 as well. So sint has to be zero, this is for t = 0 (but that couldn't be) or t = pi. Use t = pi and x will be 0 while y will be pi*cos(pi) = pi*(-1) = -pi, as was given. Then you have your t :smile:
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