放逐123456
幼苗
共回答了20个问题采纳率:75% 举报
这个用极坐标
令x=pcosa,y=psina
a∈[0,π/2]
p∈[0,1]代入得
原积分=∫[0,π/2]∫[0,1]√(1-p^2)*pdpda
=∫[0,π/2]da∫[0,1]√(1-p^2)*pdp
=π/2*(-1/2)∫[0,1]√(1-p^2)d(1-p^2)
=π/2*(-1/3)(1-p^2)^(3/2)[0,1]
=π/6
1年前
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=π/2*(-1/2)∫[0,1]√(1-p^2)d(1-p^2)
=π/2*(-1/3)(1-p^2)^(3/2)[0,1]
这两步 没太看懂