Write the Complex Number in Rectangular Form $9 \left( \cos 180 ^ { \circ } + i \sin 180 ^ { \circ } \right)$

Multiple Choice

Write the complex number in rectangular form.
- $9 \left( \cos 180 ^ { \circ } + i \sin 180 ^ { \circ } \right)$

A) $- 9$
B) $- 9 \mathrm { i }$
C) 9
D) $9 \mathrm { i }$