Originally Posted by

**mmattson07** Hey I am not sure how to find the second coordinate of these polar coordinates.

a) Find polar coordinates (*r*, *θ*) of the point (4, -4), where *r* > 0 and 0 ≤ *θ* ≤ 2*π*.

So $\displaystyle r= \sqrt{(4)^2+(4)^2}$

$\displaystyle = \sqrt{32}$

$\displaystyle =4\sqrt{2}$

I tried doing

*θ=*$\displaystyle tan^{-1}(\frac{y}{x})$

*θ=*$\displaystyle tan^{-1}(\frac{-4}{4})$

*θ=*$\displaystyle tan^{-1}(-1)$

*θ=*$\displaystyle \frac{-\pi}{4}$

But this is incorrect?

For *r* < 0 and 0 ≤ *θ* ≤ 2*π*.

$\displaystyle r=-4\sqrt{2}$

How do I find theta?