设底面半径x,
底面积,S底=(π/2)x²,
侧面积,S侧=S-S底=S-(π/2)x²,
底面周长,L=πx+2x=(π+2)x,
高,h=S侧/L=[S-(π/2)x²]/[(π+2)x],
容积关于x的函数,V(x)=S底×h=(π/2)x²[S-(π/2)x²]/[(π+2)x]=[π/(2π+4)][Sx-(π²/4)x³],
V'(x)=[π/(2π+4)][S-3(π²/4)x²],
可知x=√(4S/3π²)=(2/π)√(S/3)时,V'(x)=0,且V(x)有极大值,
V(√(4S/3π²))=2S√S/[3√3(π+2)],