If n is an integer which leaves remainder one when divided by three, then (1+√3i)n + (1-√3i)n equals
The Attempt at a Solution
Multiply and divide each of the two expression inside bracket by 2.
2n(cosπ/3 + isinπ/3)n + 2n(cosπ/3-isinπ/3)n
On simplifiying, the expression equals
2n(2cosnπ/3)=2n(-1)=-2n which is same as (d)
The correct option is (c). I have no idea where I went wrong.