### Home > PC3 > Chapter 12 > Lesson 12.1.4 > Problem12-64

12-64.

Let $z = \cos(78º) + i \sin(78º)$ and $w = 15(\cos(174º) + i\sin(174º))$. Compute:

1. $zw$

Given two complex numbers: $z_1=r_1(\cos(a) + i\sin(a))\text{ and } z_2=r_2(\cos(b) + i\sin(b))$.
The product of the two numbers $z_1z_2$ is: $z_1z_2=r_1r_2(\cos(a+b)+i\sin(a+b))$

1. $\frac { w } { z }$

The quotient of the two numbers $z_1 \text{ and } z_2$ is: $\frac{z_1}{z_2}=\frac{r_1}{r_2}(\cos(a-b)+i\sin(a-b))$