(1+cosϕ+isinϕ1+cosϕ−isinϕ)n =
[2cos2(ϕ2)+2isin(ϕ2)cos(ϕ2)2cos2(ϕ2)−2isin(ϕ2)cos(ϕ2)]n
= [2cos(ϕ2)+2isin(ϕ2)2cos(ϕ2)−2isin(ϕ2)]n = [ei(ϕ2)e−i(ϕ2)]= (eiϕ)n
=cosnϕ + isinnϕ.