Answer
$90^\circ$.
Work Step by Step
From what we learned: $\cos\theta=\frac{U\cdot V}{|U||V|}=\frac{13\cdot0+0\cdot(-6)}{\sqrt{13^2+0^2}\sqrt{0^2+(-6)^2}}=\frac{0}{13\cdot6}=0$
Thus $\theta=\cos^{-1}0=90^\circ$.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.