# Vectors – Calculate angles of a triangle – Exercise 4471

Exercise

Given

$$\vec{AB}=-2\vec{i}+\vec{j}$$

$$\vec{BC}=\vec{i}+2\vec{j}$$

Calculate the angle of triangle ABC and the vector CA.

$$45^{\circ},45^{\circ},90^{\circ}$$
$$\vec{CA}=\vec{i}-3\vec{j}$$