1 Write an equation relating the rates of change of the variables in these formulae. a Area of a circle: A = 1/2 b Surface area of a closed cylinder: A = 2ar + 2nh c Volume of a cone: V = -ar h 3 d Volume of a sphere: V = ~ xr 3 2 If I, w and h represent the length, width and height of a rectangular box, express the rate of change of the diagonal length of the box in terms of the rates of change of l, w and h