曲线y=x^2(x>=0)上某一点A(2,t),很明显A(2,4)
y'=2x=4
专心切线方程为
y-4=4(x-2)
即
4x-y-4=0
运用定积分得
∫[0,4][(y+4)/4-√y]dy
=[y^2/8+y-2/3y^(3/2)][0,4]
=2+4-16/3
=2/3