The dot product is computed between two vectors.
For these use cases that dot product is equal to the cosine of the angle between these angles.
(Strictly speaking we have that the angle is actually defined in terms of the dot/inner product in more abstract spaces like function spaces or L^p/l^p)
(Strictly speaking we have that the angle is actually defined in terms of the dot/inner product in more abstract spaces like function spaces or L^p/l^p)