被积函数分子分母除以x²有
∫(x^2+1)/(x^4+1)dx = ∫(1+1/x²)/(x²+1/x²)dx
令u=x-1/x ,则 du = (1+1/x²)dx
且 u² = x²+1/x² -2
则原式= ∫ du/(u²+2)
=1/根号2 * arctan (u/根号2)
再u=x-1/x代进去