(i) z=4(cos5π3+isin5π3)z=4\left(\cos\frac{5\pi}{3}+i\sin\frac{5\pi}{3}\right)z=4(cos35π+isin35π) cos5π3=12,sin5π3=−32\cos\frac{5\pi}{3}=\frac{1}{2},\quad \sin\frac{5\pi}{3}=-\frac{\sqrt{3}}{2}cos35π=21,sin35π=−23 z=4(12−32i)=2−23 i\boxed{z=4\left(\frac{1}{2}-\frac{\sqrt{3}}{2}i\right)=2-2\sqrt{3}\,i}z=4(21−23i)=2−23i