详情见图 , 给个答案, 大哥大姐,

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详情见图 , 给个答案, 大哥大姐,
详情见图 , 给个答案, 大哥大姐,

详情见图 , 给个答案, 大哥大姐,
极坐标:
x = rcosθ,
y = rsinθ
极坐标下区域D: 0≤θ≤π/4 ,1≤r≤2
被积函数:y/x = tanθ ( 0≤θ≤π/4 )
arctan(y/x) = arctan(tanθ) = θ (0≤θ≤π/4)
∫∫D arctan(y/x) dσ
=∫[0,π/4] dθ ∫[1,2] rθ dr
=∫[0,π/4] θdθ ∫[1,2] r dr
= {θ|[0,π/4]}*{1/2r^2|[1,2]}
=π/4*3/2
= 3π/8