`I =int(x^(2)-1)/((x^(2)+1)sqrt(x^(4)+1))dx` `=int(x^(2)(1-1//x^(2)))/(x^(2)(x+1//x)sqrt(x^(2)+1//x^(2)))dx` `=int((1-1//x^(2))dx)/((x+1//x)sqrt((x+1//x)^(2)-2))` Putting `x+1//x=t,` we have `I=int(dt)/(t sqrt(t^(2)-2)).` Again putting `t^(2)-2=y^(2), 2tdt=2ydy,` `I=int(ydy)/((y^(2)+2)y)=(1)/(sqrt(2))"tan"^(-1)(y)/(sqrt(2))=(1)/(2)"tan"^(-1)sqrt(x^(2)+1//x^(2))/(sqrt(2))+c.`