Posted by mark on Saturday, September 20, 2008 at 8:47pm.
the path of a particle in the xyplane is vector r = (cos2t, sint) for t for all [pi/2, pi] where t represents time. Sketch the path. Is it a smooth curve?
How do i sketch the path? do i just plug in random points between [pi/2, pi]? how would i connect it together? and how do i know if it's a smooth curve? Thank you.

calculus  drwls, Sunday, September 21, 2008 at 12:18am
When t = pi/2, x = cos(pi) = 1 and y = sin pi/2 = 1
When t = pi/4, x = cos(pi/2) = 0 and y = sin pi/4 = 0.707
When t = 0, x = 1 and y = 0
When t = pi/4, x = 0 and y = .707
When t = pi/2, x = 1 and y = 1
When t = 3pi/4, x = cos 3pi/2 = 0 and y = sin3pi/4 = 0.707
When t = pi, x = 1 and y = 0
The particle follows a smooth curve. The curve looks like a parabola that is open to the left.
You can use a trigonometric identity to show that the curve is
x = 1  2y^2, which is indeed a parabola.

calculus  mark, Sunday, September 21, 2008 at 4:19pm
wow thx a lot man
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