1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    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:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook