Question

Express the complex number in trigonometric form.

-4

Answer 1

4(cos 270degrees + i sin 270degrees)

4(cos 90degrees + i sin 90degrees)

4(cos 0degrees + i sin 0degrees)

4(cos 180degrees + i sin 180degrees)

Answer 2

@AnswerMyQuestions @mathmath333 any help?

Answer 3

No @mathmath333

Answer 4

I'm not good at this stuff...

Answer 5

\(-4i\)

Answer 6

\(\Huge ?\)

Answer 7

It's just -4

Answer 8

-4 cannot be a complex number

it is a real number

Answer 9

or better u post a screen shot of question

Answer 10

Okay I'll do that

Answer 11

@mathmath333 here it is

Answer 12

well i think its a typo their
it should be \(\large -4i\) or something else

Answer 13

in question 4 also,it their also only digit or \(\large i\) also

Answer 14

Okay well I guess and it was wrong. I don't know what the question meant but I got it wrong anyway. Thanks for your help.

Answer 15

A medal for your troubles

Answer 16

here is a solution if it is \(\large -4i\)



\(\large \tt \begin{align} \color{black}{z=a+bi\\~\\
r=|z|=\sqrt{a^2+b^2}\\~\\
\alpha=tan^{-1}(\dfrac{b}{a})\\~\\
trig form \\~\\
z=r(cos\alpha+isin\alpha)\\~\\
z=0-4i\\~\\
r=\sqrt{(-4)^2}=4\\~\\
\alpha=tan^{-1}\dfrac{-4}{0}=tan^{-1}(-\infty)=-\dfrac{\pi}{2}\\~\\
z=4[cos(-90)+isin(-90)]\\~\\
z=4[(cos(270)+isin(270)]
} \end{align}\)


so option \(\huge A\) is correct

Answer 17

That's exactly the one I guessed and it was wrong

Answer 18

thats strange!!!