CPM Homework Help : PC3 Problem 8-80

Calculate the angle between each pair of vectors below.

$3 \mathbf{\text{i}} + 4 \mathbf{\text{j}}$ and $-2\mathbf{\text{j}}$
Hint (b):
These vectors are $⟨3, 4⟩$ and $⟨0, −2⟩$ .