x^2+y^2=a^2,y^2+z^2=a^2三重积分算体积
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x^2+y^2=a^2,y^2+z^2=a^2所围体积,考虑对称性,每个卦限体积相等,只要还求出第一卦限体积再乘以8即可,

积分区域Ω,在ZOY平面投影是1/4圆,0≤y≤a,

0≤z≤√(a^2-y^2),

0≤x≤√(a^2-y^2),即下限为x=0的平面(YOZ平面),上限为√(a^2-y^2)的柱面,

V=8∫[0,a]dy∫[0,√(a^2-y^2)]dz∫[0,√(a^2-y^2]dx

=8∫[0,a]dy∫[0,√(a^2-y^2)](√(a^2-y^2)dz

=8∫[0,a] (a^2-y^2)dy

=8(a^2y-y^3/3) [0,a]

=16a^3/3.