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关键步骤:区域D:{(x,y)|0<=x<=π/2,x<=y<=π/2}也可以写成D:{(x,y)|0<=y<=π/2,0<=x<=y}(化出图来一目了然,是同一个三角形)。
所以
∫(上限π/2,下限0)(∫(上限π/2,下限x)siny/y
dy)dx
=(f(x,y)=siny/y在D上的二重积分)
=∫(上限π/2,下限0)(∫(上限y,下限0)siny/y
dx)dy
=∫(上限π/2,下限0)((y-0)*siny/y)dy
=∫(上限π/2,下限0)siny
dy
=-cos(π/2)+cos(0)
=1
所以
∫(上限π/2,下限0)(∫(上限π/2,下限x)siny/y
dy)dx
=(f(x,y)=siny/y在D上的二重积分)
=∫(上限π/2,下限0)(∫(上限y,下限0)siny/y
dx)dy
=∫(上限π/2,下限0)((y-0)*siny/y)dy
=∫(上限π/2,下限0)siny
dy
=-cos(π/2)+cos(0)
=1
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