I want to know how to solve such questions:
1) The radius of a cylinder is increasing at the rate of and the volume is decreasing at the rate of . where and , find the rates of change of:
(i) the height
(ii) the surface area
Note that and
2) The region in the first quadrant is bounded by the y-axis, the line y=x and the curve . Calculate the volume formed when R is rotated about the y-axis through 1 revolution.
(what should I do after finding the area? )