Answer
$(3 \sqrt 2, \dfrac{7 \pi}{4})$
Work Step by Step
Here, $r=\sqrt {x^2+y^2}=\sqrt{(3)^2+(-3)^2}=3 \sqrt 2$
$\tan \theta =\dfrac{y}{x}$
and $\theta=arctan[\dfrac{3}{-3}]=arctan {-1}$
Thus, $\theta =\dfrac{7 \pi}{4}$
Hence, $(3 \sqrt 2, \dfrac{7 \pi}{4})$