Question

WILL GIVE BRAINLEST ANSWER IF ANSWERED IN THE NEXT 24 HRS Express the complex number in trigonometric form. -5i

Answer 1

Answer:

in degrees the answer is 5 (cos 270 + i sin 270)

in radians the answer is 5 (cos (3pi/2) + i sin (3pi/2))

Step-by-step explanation:

Answer 2

Answer:

$z=5\left(\cos \left(\dfrac{3\pi}{2}\right)+i\sin \left(\dfrac{3\pi}{2}\right)\right)$

Step-by-step explanation:

If a complex number is z=a+ib, then the trigonometric form of complex number is

$z=r(\cos \theta +i\sin \theta)$

where, $r=\sqrt{a^2+b^2}$ and $\tan \theta=\dfrac{b}{a}$, $\theta$ is called the argument of z, $0\leq \theta\leq 2\pi$.

The given complex number is -5i.

It can be rewritten as

$z=0-5i$

Here, a=0 and b=-5. $\theta$ lies in 4th quadrant.

$r=\sqrt{0^2+(-5)^2}=5$

$\tan \theta=\dfrac{-5}{0}$

$\tan \theta=\infty$

$\theta=2\pi -\dfrac{\pi}{2}$    $[\because \text{In 4th quadrant }\theta=2\pi-\theta]$

$\theta=\dfrac{3\pi}{2}$

So, the trigonometric form is

$z=5\left(\cos \left(\dfrac{3\pi}{2}\right)+i\sin \left(\dfrac{3\pi}{2}\right)\right)$