let x = tan t
then dx = sec^2 t dt
sec^2 t dt/[ tan t (1+tan^2 t) ]
NOTE: 1+tan^2 t = sec^2 t !!! wow that helps :)
so we have
dt/tan t = ctn t dt
= ln (sin u)
Integrate 1/(x(x^2+1)) dx
using trig substitution
1 answer