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

Question

Quizplus · Accepted Answer

The given complex number is in polar form. Using the identities $\cos 180^\circ = -1$ and $\sin 180^\circ = 0$, the complex number can be written as $9(-1 + 0i)$, which simplifies to $-9$.

Write the Complex Number in Rectangular Form 9(cos⁡180∘+isin⁡180∘)9 \left( \cos 180 ^ { \circ } + \mathrm { i } \sin 180 ^ { \circ } \right)9(cos180∘+isin180∘)

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