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

Question

Quizplus · Accepted Answer

The given complex number is in polar form. Using the trigonometric values, $\cos 180^\circ = -1$ and $\sin 180^\circ = 0$, the complex number becomes $9(-1 + 0i) = -9$.

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

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