Question

Convert Зcis 180° to rectangular form. А. -3 в. -3i с. з D. Зі.

Answer 1

Answer:

-3

Step-by-step explanation:

$3 cis(180^\circ)$ means $3(\cos(180^\circ)+i \sin(180^\circ))$

What is the $x$-coordinate value that corresponds to $\theta=180^\circ$. That value is -1.

What is the $y$-coordinate value that corresponds to $\theta=180^\circ$. That value is 0.

So this implies $\cos(180^\circ)=-1 \text{ and } \sin(180^\circ)=0$.

$3 cis(180^\circ)$  

$3(\cos(180^\circ)+i \sin(180^\circ))$

$3(-1+i (0))$

$3(-1+0)$

$3(-1)$

$-3$