Calculate the Angle Between $\mathbf { a }$ And $\mathbf { b }$

Short Answer

Calculate the angle between $\mathbf { a }$ and $\mathbf { b }$ (correct to the nearest degree).
$$\mathbf { a } = 3 \mathbf { i } - 2 \mathbf { j } , \mathbf { b } = - 7 \mathbf { j } + \mathbf { k }$$