设x=rcosθ,y=rsinθ (极坐标代换)
原式=∫(0,π/2)dθ∫(0,1)sin(1+r²)rdr (符号∫(0,π/2)表示从0到π/2积分,其它类同)
=(2π)/2∫(0,1)sin(1+r²)d(1+r²)
=[π(-1)cos(1+r²)]│(0,1)
=-π[cos(1+1²)-cos(1+0²)]
=π(cos1-cos2).
设x=rcosθ,y=rsinθ (极坐标代换)
原式=∫(0,π/2)dθ∫(0,1)sin(1+r²)rdr (符号∫(0,π/2)表示从0到π/2积分,其它类同)
=(2π)/2∫(0,1)sin(1+r²)d(1+r²)
=[π(-1)cos(1+r²)]│(0,1)
=-π[cos(1+1²)-cos(1+0²)]
=π(cos1-cos2).