Posted by **Kristin** on Sunday, September 25, 2011 at 3:02pm.

The position vector r of a particle moving in an xy plane is given by [r = (6t^3-3t)i + (4-1t^4)j] with r in meters and t in seconds. What is the angle between the positive direction of the x axis and a line tangent to the particle's path at t = 3 s? Give your answer in the range of (-180 degrees; 180 degrees].