Centroid question first (#6):
Find the x coordinate of the centroid of the area bounded by y = 1/(1+(x^2)) - 1/5, the x-axis, y-axis in the first quadrant.
using formula x = (int) (x(y^2)dx) / ((y^2)dx)
I would plug in the y equation as in problem statement and integrate, however unsure of how to integrate 1/5. Got the feeling I'm missing something really simple here.

Unknown question (#3):
Please help me identify whether they are looking for a derivative or integral:
The hypocycloid equation of an object is expressed by the parametric form x = r cos^3 and y = r sin^3 . The constant r = 0.25 m and the angular velocity d/dt = 0.5 rad/s when = 30 degrees. Find the velocity of the object at this instant.

So is this a related rate question?