سیگما

`Q=int (dx)/sqrt(tanx)`
`x=u/2`
`(dx)/(du)=1/2`
`Q=1/2 int (du)/sqrt(tan(u/2))`
`tan(u/2)=t`
`du=(2dt)/(1+t^2)`
`Q=1/2 int (2/(1+t^2))/(sqrt(t)) dt`
`Q=int (dt)/(sqrt(t)(1+t^2))`
`p^2=t`
`(dt)/(dp)=2p`
`Q=int (2p)/(p(1+p^4)) dp`
`Q=2 int (dp)/(p^4+1)`
`hal shode`
`link`
`2(sqrt(2)/8(ln((p^2+sqrt(2)p+1)/(p^2-sqrt(2)p+1))+2arctan(sqrt(2)p+1)-2arctan(1-sqrt(2)p)))`
`p=sqrt(tanx)`