Assuming your last line is correct (and I haven't bothered to check) then you can use deMoivre's Theorem to write . Now expand and group the real and imaginary parts.
Assuming your last line is correct (and I haven't bothered to check) then you can use deMoivre's Theorem to write . Now expand and group the real and imaginary parts.
U are missing the question if u look closely the last line is