Dot product of 2 vectors

Dot product of 2 vectors $v1$ and $v2$ is defined as $|v1||v2|cos(\theta )$.
Or if the vectors are written as components $v1=(v{1}_x,v{1}_y,v{1}_z,...)$, $v2=(v{2}_x,v{2}_y,v{2}_z,...)$ then the dot product is just the sum of product of all the components, $v{1}_{x}v{2}_x+v{1}_{y}v{2}_y+v{1}_{z}v{2}_z+...$