+118687 \(120^\circ=\frac{2\pi}{3}\;radians\)
hint:
(this example is a bit harder than your ones but the method is the same.)
\(A=2.5e^{\frac{2\pi}{3}i}\\ A=2.5[(cos\frac{2\pi}{3})+isin(\frac{2\pi}{3})]\\ A=2.5[-(cos\frac{\pi}{3})+isin(\frac{\pi}{3})]\\ A=2.5[-(\frac{\sqrt3}{2})+i(\frac{1}{2})]\\ A=1.25[-(\sqrt3)+i)]\\ A=-1.25\sqrt3+1.25i\\\)
