def cross(triangles):
    """
    Returns the cross product of two edges from input triangles

    Parameters
    --------------
    triangles: (n, 3, 3) float
      Vertices of triangles

    Returns
    --------------
    crosses : (n, 3) float
      Cross product of two edge vectors
    """
    vectors = np.diff(triangles, axis=1)
    crosses = np.cross(vectors[:, 0], vectors[:, 1])
    return crosses