I am not sure about the 'best, way to do this but
$$\\r=\sqrt{4+9}=\sqrt{13}\\
tan\theta=3/2\\$$
$$\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{tan}}^{\!\!\mathtt{-1}}{\left({\mathtt{1.5}}\right)} = {\mathtt{56.309\: \!932\: \!474\: \!02^{\circ}}}$$
$$(2,3)\approx(\sqrt{13}, 56.3^0)$$
I think that is correct :)
