Polar form of a complex number

[mandy]

Express the following complex number in polar form.

-1-i

The answer I got was ()

The actual correct answer is meant to be ()

Was I meant to do that whole minus the answer thing? If so, how do I know when I have to minus and when I can just leave it as is?

[TrueTears]

Remember -1-i is in the 3rd quadrant, so you need to do assuming principle argument.

[kamil9876]

best way is to just plot it on the argand diagram and just work it out from there. Using is dangerous since and so you could mistakenly show that .

[TrueTears]

... In other words, just remember to sketch the point on the argand diagram to know what quadrant it is in.

[mandy]

okay, thanks, i'll remember that.

How would I convert 3i to polar form?
Because when I find the tan , doesnt it equal undefined?

[TrueTears]

Don't just keep thinking about tan, remember a picture tells a thousand words.

Sketch a diagram of the point 3i what do you notice?

You can clearly see the angle is \frac{\pi}{2} and it has a magnitude of 3.

[kamil9876]

that's why you should forget about and just draw, you now been shown two instances of it's incompleteness(This applies to many situations that involve inverse circular functions, just draw). drawing , you see that the argument would be (edited, won't show answer)

[mandy]

okay, i understand. its just the teacher didn't teach us the drawing way, so i had no idea i could do that.
thanks