高校问答股指期货是t 0还是t 1:见补充说明
来源：百度文库 编辑：高校问答 时间：2024/04/27 20:23:55
air is pumped into a spherical ball which expands at a rate of 8 cm^3 per second. find the exact rate of increase of the radius of the ball when the radius if 2 cm.（cm^3=三立方厘米）
air is pumped into a spherical ball which expands at a rate of 8 cm^3 per second. find the exact rate of increase of the radius of the ball when the radius is 2 cm.
V = (4/3)*pi*r^3 cm^3
dV/dr = 4*pi*r^2
dr/dV = 1/(4*pi*r^2)
dr/dt = (dr/dV)*(dV/dt) = 8/(4*pi*r^2)
when r is 2, the rate of increase of radius = 8/(4*pi*2^2) = 1/(2*pi).
看的懂不?