Find the trigonometric form of the complex number shown below. $- 7 i$
A) $7 ( \cos 0 + i \sin 0 )$
B) $7 ( \cos \pi + i \sin \pi )$
C) $7 \left( \cos \frac { 3 \pi } { 2 } + i \sin \frac { 3 \pi } { 2 } \right)$
D) $7 \left( \cos \frac { \pi } { 4 } + i \sin \frac { \pi } { 4 } \right)$
E) $7 \left( \cos \frac { \pi } { 2 } + i \sin \frac { \pi } { 2 } \right)$

Question

Quizplus · Accepted Answer

The trigonometric form of a complex number is $r(\cos \theta + i\sin \theta)$, where $r$ is the magnitude of the complex number and $\theta$ is the argument. For $-7i$, $r = 7$ and the argument $\theta = \frac{3\pi}{2}$, because the point lies on the negative imaginary axis.

Find the Trigonometric Form of the Complex Number Shown Below −7i- 7 i−7i

Find the Trigonometric Form of the Complex Number Shown Below $- 7 i$