Express the complex number in trigonometric form.

-3i

Question

Express the complex number in trigonometric form.

-3i

jhhhhhiiiii · Answer

@baru can you help with this one and just one more?

baru · Answer

think of it as:
0+3i

can you find its magnitude?

jhhhhhiiiii · Answer

3?

baru · Answer

yep,
so that complex number in trignometric form looks this way:
$$3(\cos \theta + i \sin \theta)$$

so i'm just going to factor out 3 from 0 + 3i
to get
3(0 + i)

so now the problem reduces to finding $\theta$ such that $cos \theta=0$ and $sin \theta = 1$ 

so what is the value of $\theta$ ?

jhhhhhiiiii · Answer

I'm not sure..

baru · Answer

look it up here: http://www.mathwords.com/t/t_assets/t80.gif

baru · Answer

you just need to find $\theta$ such that cos$\theta$=0

jhhhhhiiiii · Answer

0?

baru · Answer

is cos(0) = 0 ?

jhhhhhiiiii · Answer

yes

baru · Answer

http://www.mathwords.com/t/t_assets/t80.gif look it up in that link, what is the value of cos(0) ?

jhhhhhiiiii · Answer

It's 1?

jhhhhhiiiii · Answer

Idk I'm sorry I'm not good at this

phi · Answer

one way to find the angle is to plot the point (x is the real part and y is the complex part)
in other words, think of 0-3i  as  (0, -3)
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