# Question #3597d

$| | B | | \cos \theta$ is the projection of $\vec{B}$ along the direction of $\vec{A}$.
The scalar (dot) product of $\vec{A}$ and $\vec{B}$ is defined by
$\vec{A} \cdot \vec{B} = A B \cos \theta$
where $A$ and $B$ are the respective magnitudes of $\vec{A}$ and $\vec{B}$ and $\theta$ is the angle between $\vec{A}$ and $\vec{B}$.