设∑为上半球面x2+y2+z2=a2d的外侧,则∫∫zdxdy=____.
设∑为上半球面x2+y2+z2=a2d的外侧,则∫∫zdxdy=____.
【正确答案】:∫∫zdxdy=∫∫D√(a2-x2-y2)•[a/√(a2-x2-y2)]dxdy=(2/3)πa3
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