令a=x²原式=1/2*∫dx²/(x^4+2x²+5)=1/2*∫da/(a²+2a+1+4)=1/2*∫da/[(a+1)²+4]=1/8*∫da/[(1/4)(a+1)²+1]=1/8*∫da/[(a/2+1/2)²+1]=1/4*∫d(a/2+1/2)/[(a/2+1/2)²+1]=1/4*a...