Hey there,
First, find the square root of the given equation.
[tex]\sqrt{z}=\sqrt{81(\text{cos}(\frac{4\pi}{9})+i\text{sin}(\frac{4\pi}{9})}\\=9\text{cos}\frac{1}{2}(2k\pi+(\frac{4\pi}{9}))+i\text{sin}\frac{1}{2} (2k\pi+(\frac{4\pi}{9}))[/tex]
Keep in mind that this is solved for k = 0 and 1.
Second, simplify.
[tex]=9\text{cos}(\frac{2\pi}{9})+i\text{sin}(\frac{2\pi}{9})~\text{or}~9\text{cos}(\frac{11\pi}{9})+i\text{sin}(\frac{11\pi}{9})[/tex]
Best of Luck!
