Chapter 9 - Polar Coordinates; Vectors - 9.3 The Complex Plane; De Moivre's Theorem - 9.3 Assess Your Understanding - Page 594: 44

$-\frac{27}{2}+i\frac{-27\sqrt3}{2}.$

Using De Moivre's Theorem ($(\cos{x}+i\sin{x})^n=\cos{nx}+i\sin{nx}.$): $[3(cos(80^\circ)+i(sin(80^\circ))]^3=3^3(cos(3\cdot80^\circ)+i(sin(3\cdot80^\circ)))=27\cdot(cos(240^\circ)+i(sin(240^\circ)))=27\cdot(-\frac{1}{2}+i\frac{-\sqrt3}{2})=-\frac{27}{2}+i\frac{-27\sqrt3}{2}.$