関連ワード:  integral 1/(1+x^2) dx    integral 1 1 x 2 dx    what is the integral of 1/(1+x^2)    integral of 1/(x^2-25)    integration of 1 /(x^2- a^2) dx    what is the integral of 1/x^2    what is the integral of 1/(1-x)