设半径为r2*π*r²+2*π*h-2*π*h=2*π*r²=12.56r²=2,r=2^0.5V=π*r²*h=3.14*2*5=31.4dm²或者2*底面积+侧面积-侧面积=12.56底面积=12.56/2=6.28体积=底面积*5=6.28*5=31.4dm²...