def dot(vec_1, vec_2):
    """
    From two vectors calculate and return the dot product. This
    is also know as the inner product and is scalar value (that represents
    the product of the magnitudes of the two vectors and the cosine of the
    angle between them).

    :param vec_1: a subscriptable collection of length 3
    :param vec_2: a subscriptable collection of length 3
    :return dot_product: scalar value (float)
    """

    # Using cartesian coordinates, calculate the dot product
    dot_product = vec_1[0] * vec_2[0] + vec_1[1] * vec_2[1] + vec_1[2] * vec_2[2]

    return dot_product