Step 1 :\( r = \sqrt{x^2 + y^2} = \sqrt{6^2 + (-13)^2} \)
Step 2 :\( \theta = \tan^{-1}(\frac{y}{x}) = \tan^{-1}(\frac{-13}{6}) \)
Step 3 :\( \left(r, \, \theta \right) = \left(\sqrt{6^2 + (-13)^2}, \, \tan^{-1}(\frac{-13}{6}) \right) \)