Posted by Catherine on Friday, April 15, 2011 at 1:10am.
A particle moves with its position given by x=cos(2t) and y=sin(t), where positions are given in feet from the origin and time t is in seconds.
A)Find the speed of the particle.
Speed = ____________
(include units)
B)Find the first positive time when the particle comes to a stop.
t=_____
(include units)
C)If n is any odd integer, write a formula (in terms of n) for all positive times t at which the particle comes to a stop.
t=______
(include units)
For the first one I got sqrt((2sin(2t))^2+(cos(t))^2) ft/s.
I don't know ho to calculate the second and third part... please someone help...

Calculus (urgent!!)  MathMate, Friday, April 15, 2011 at 10:31am
x=cos(2t) and y=sin(t)
x'(t)=2sin(2t),
y'(t)=cos(t)
A.
Speed at time t (in ft/sec)
= sqrt(x'(t)²+y'(t)²)
= sqrt(4sin²(2t)+cos²(t))
= ... simplify as you wish
B.
x'(t)=2sin(2t)=0
occurs when t=kπ/2, k∈Z
and y'(t)=cos(t)=0
occurs when t=(k+1/2)π, k∈Z
So what is the smallest t when x'(t)=0 AND y'(t)=0?
C.
Work out from B above.
Post if you more hint.
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