Cross product of two vectors, v1 x v2
    
    Parameters
    ----------
    x1 : float or array-like
        X component of vector 1
    y1 : float or array-like
        Y component of vector 1
    z1 : float or array-like
        Z component of vector 1
    x2 : float or array-like
        X component of vector 2
    y2 : float or array-like
        Y component of vector 2
    z2 : float or array-like
        Z component of vector 2
        
    Returns
    -------
    x, y, z
        Unit vector x,y,z components

def cross_product(x1, y1, z1, x2, y2, z2):
    """
    Cross product of two vectors, v1 x v2
    
    Parameters
    ----------
    x1 : float or array-like
        X component of vector 1
    y1 : float or array-like
        Y component of vector 1
    z1 : float or array-like
        Z component of vector 1
    x2 : float or array-like
        X component of vector 2
    y2 : float or array-like
        Y component of vector 2
    z2 : float or array-like
        Z component of vector 2
        
    Returns
    -------
    x, y, z
        Unit vector x,y,z components
        
    """
    x = y1*z2 - y2*z1
    y = z1*x2 - x1*z2
    z = x1*y2 - y1*x2
    return x, y, z