Are you aware of De-Moivre's theorem and how to use that to solve roots for z^n = 1?
I dont understand what yuo did in 8th step, how you expanded it?
other thing, did you read the solution i posted? there its done in almost 5 steps :P
actually what i wanted to ask and i was stuck on this step
how does the following happen?
in solution it says "cis" where i have put cos, as i was thinking it was a typo in solution but if there is something as cis do let me know