One of my homework questions on WebAssign asks that I convert the point $(-5, 5, 5)$ from rectangular to cylindrical coordinates such that $r\geq 0$ and $0 \leq \theta \leq 2\pi $.
Seems pretty straightforward, but the system won't accept my answer.
My approach
$r = \sqrt{x^2 + y^2} = \sqrt{25 + 25} = \sqrt{2(25)} = 5\sqrt2$
$\theta = arctan(5/-5) = -\pi/4 = 7\pi/4$ (since they want $\theta $ to be positive)
$z = z = 5$
Wouldn't the point be $(r, \theta, z) = (5\sqrt2, 7\pi/4, 5)$? Did I make a mistake somewhere?