∫∫D[(1-x2-y2)/(1+x2+y2)]dσ,其中D是
x2+y2=1,x=0,y=0所围第I象限内的部分.
∫∫D[(1-x2-y2)/(1+x2+y2)]dσ= ∫0π/2dθ∫01[(1-r2)/(1+r2)]rdr= π/2∫01[2/(1+r2)-1]rdr =π/2[ln(1+r2)∣01-(1/2)r2∣01] =π/2(ln2-1/2)
∫∫D[(1-x2-y2)/(1+x2+y2)]dσ,其中D是
x2+y2=1,x=0,y=0所围第I象限内的部分.
∫∫D[(1-x2-y2)/(1+x2+y2)]dσ= ∫0π/2dθ∫01[(1-r2)/(1+r2)]rdr= π/2∫01[2/(1+r2)-1]rdr =π/2[ln(1+r2)∣01-(1/2)r2∣01] =π/2(ln2-1/2)