Question

Vector A has magnitude 4.0 units and vector B has magnitude 5.0 units. The angle between A and B is 60.0°. What is the magnitude of A+B ?

Answer 1

The magnitude is

$$|A+B|=\sqrt{(A+B\cos\theta)^2+(B\sin\theta)^2},\\ A+B|=7.8\text{ units}.$$