设∑为球面x2+y2+z2=1的下半部分的下侧，则∫∫∑zdxdy=()
A.-∫02πdθ∫01(√1-r2)•rdr B.∫02πdθ∫01(√1-r2)•rdr C.-∫02πdθ∫01(√1-r2)dr D.∫02πdθ∫01(√1-r2)dr正确答案B
设∑为球面x2+y2+z2=1的下半部分的下侧，则∫∫∑zdxdy=()
A.-∫02πdθ∫01(√1-r2)•rdr B.∫02πdθ∫01(√1-r2)•rdr C.-∫02πdθ∫01(√1-r2)dr D.∫02πdθ∫01(√1-r2)dr正确答案B
