ok i'm having trouble with this problem...
i think there must be a very easy way of doing it but i'm just not getting it.....( i ended up in a huge mess)
tan(4x)=1.....sounded really easy to me!
and i used the same expansion method to expand cos(4x) and tried to solve but i still don't see the answer which has to be solved algebrically (Crying)
help is appreaciated...