The rate of change of radius of a spherical air bubble is 0.002 cm/s. What is the rate of change of its surface area when its radius is 2 cm?
a = 4pi r^2
da/dt = 8pi r dr/dt
when r=2,
da/dt = 8pi * 2 * .002 = .032pi
da/dt = 8pi r dr/dt
when r=2,
da/dt = 8pi * 2 * .002 = .032pi