The value of $\left({1+\sin{2\pi\over9}+i\cos{2\pi\over9}\over1+\sin{2\pi\over9}-i\cos{2\pi\over9}}\right)^3$ is :

(1) $-{1\over2}(\sqrt3-i)$

(2) ${1\over2}(\sqrt3-i)$

(3) ${1\over2}(1-i\sqrt3)$

(4) $-{1\over2}(1-i\sqrt3)$

(1) $-{1\over2}(\sqrt3-i)$

(2) ${1\over2}(\sqrt3-i)$

(3) ${1\over2}(1-i\sqrt3)$

(4) $-{1\over2}(1-i\sqrt3)$