∫ 1/(x^2+1)^2的定积分求解.也就是∫1/(x^4+2x^2+1)
问题描述：
∫ 1/(x^2+1)^2的定积分求解.也就是∫1/(x^4+2x^2+1)
答
x=tant
∫ 1/(x^2+1)^2dx
=∫ 1/(tant^2+1)^2dtant
=∫1/sec^4 * sec^2dt
=∫1/sec^2dt
=∫cos^2dt
=t/2+1/4sin2t +C