x=tant
x^2+1=(sec^2)t
dx=(sec^2)tdt
[1/{tan^2t*sect)] sec^2tdt
=积分 sect/tan^2t dt
=积分cost*sin^(-2)t dt
=1/sint
cos^2t=1/(1+x^2)
sin^2t=x^2/(1+x^2)
1/sint=根(1+x^2)/x
x=tant
x^2+1=(sec^2)t
dx=(sec^2)tdt
[1/{tan^2t*sect)] sec^2tdt
=积分 sect/tan^2t dt
=积分cost*sin^(-2)t dt
=1/sint
cos^2t=1/(1+x^2)
sin^2t=x^2/(1+x^2)
1/sint=根(1+x^2)/x