I'm still lost.. this is what i have after replacing all the cos@:
\frac{(2t^2+2t^4)dt}{(1-t^2)^2}
This is what i have to integrate right?
I tried to use integration by parts uv-|vdu. it gets very long and i got stuck when i have to integrate ln(1-t^2).
this is wot i got after substituting the cos(\theta) :
t^2(1+t^2)^2/(1-t^2)^2
and i got sin@^2 (cos@+1)^2/16cos@ after substituting back the
t=\tan(\theta/2)
and playing ard with it
Btw i do not understand change dx, cos i have no dx, only d\theta :