For questions 16 - 19, write each expression in the standard form for the complex number a + bi.

16. [4(cos)(7pi/9)+isin(7pi/9))]^3 Use De Moivre's theorem for roots:

17. [1/2(cos(72degrees)+isin(72degrees ))]^5 Use De Moivre's theorem for roots:

18. the complex fifth roots of 5-5 radical3i

19. find all seventh roots of unity and sketch them on the axes below

\f