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: Drawing plane curve of r(t) = <cos(t),sin(t)> have answer, confuseD!

  1. Oct 2, 2005 #1
    Hello everyone, I'm confused on this problem. It says (a) sketch the plane curve with the given vector equatiion. (b) find r'(t) which is easy. (c)Sketch the position vector r(t) and the tagent vector r'(t) for the given value of t.

    r(t) = <cos t, sin t>, t = PI/4;
    I got part b of course. But i'm stuck on how they they got part a and c. How did they get a circle, and how did they know the circle is going counter clock wise? Thanks. Here is my work:
    http://img134.imageshack.us/img134/8246/w00ta0qt.jpg [Broken]
     
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Oct 2, 2005 #2

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    As for a), what is [itex]x(t)^{2}+y(t)^{2}[/itex]?
    As for c), what is [itex]\vec{r}(\frac{\pi}{4})[/itex] and [itex]\frac{d\vec{r}}{dt}(\frac{\pi}{4})[/tex]?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook