(iii) z1⋅z2z_1\cdot z_2z1⋅z2 z1z2=45(cos19π12+isin19π12)z_1z_2=45\left(\cos\frac{19\pi}{12}+i\sin\frac{19\pi}{12}\right)z1z2=45(cos1219π+isin1219π) cos19π12=6−24,sin19π12=−6+24\cos\frac{19\pi}{12}=\frac{\sqrt{6}-\sqrt{2}}{4},\quad \sin\frac{19\pi}{12}=-\frac{\sqrt{6}+\sqrt{2}}{4}cos1219π=46−2,sin1219π=−46+2 z1z2=45(6−2)4−45(6+2)4i\boxed{z_1z_2=\frac{45(\sqrt{6}-\sqrt{2})}{4}-\frac{45(\sqrt{6}+\sqrt{2})}{4}i}z1z2=445(6−2)−445(6+2)i