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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def coords_to_vec(lon, lat):
 """ Converts longitute and latitude coordinates to a unit 3-vector return array(3,n) with v_x[i],v_y[i],v_z[i] = directional cosines """

    phi = np.radians(lon)
    theta = (np.pi / 2) - np.radians(lat)
    sin_t = np.sin(theta)
    cos_t = np.cos(theta)

    xVals = sin_t * np.cos(phi)
    yVals = sin_t * np.sin(phi)
    zVals = cos_t

    # Stack them into the output array
    out = np.vstack((xVals, yVals, zVals)).swapaxes(0, 1)
    return out