Answer:
-1.
Step-by-step explanation:
1) according to the DeMoivre's theorem:
[tex]1*(cos\frac{ \pi}{6} +isin\frac{ \pi}{6})^{18}=1^{18}(cos(18*\frac{ \pi}{6})+isin(18*\frac{ \pi}{6}))=cos3\pi +isin3\pi =cos\pi +isin\pi ;[/tex]
2) if cos(π)=-1 and sin(π)=0, then cosπ+i*sin(π)=-1.
