What is the angle between $\hat{i} - \hat{j}$ and $\hat{j} - \hat{k}$?

Explanation

1. 01

   $\vec{a} \cdot \vec{b} = 0 - 1 + 0 = -1$, and each magnitude is $\sqrt{2}$.

2. 02

   $\cos \theta = -\frac{1}{2}$, so $\theta = \frac{2\pi}{3}$.