s=xy+（π（x/2)^2）/2
y=s/x-πx/8
C=π(x/2)+x+2y=πx/2+x+2s/x-πx/4=(1+π/4)x+2s/x
(1+π/4)x=2s/x
x^2=2s/(1+π/4)
x=√(10/(1+π/4))=2.367m
解这道求最小值的应用题应该用矩形面积公式求导,还是应该用矩形周长公式求导?
s=xy+（π（x/2)^2）/2
y=s/x-πx/8
C=π(x/2)+x+2y=πx/2+x+2s/x-πx/4=(1+π/4)x+2s/x
(1+π/4)x=2s/x
x^2=2s/(1+π/4)
x=√(10/(1+π/4))=2.367m