For the divergence and consolidation divergence, the former is of the most basic significance, while the latter is just a generalized usage of the corresponding force analysis method of the former, which is mainly used in the force comparison related to the central oscillation. Note that in a+B+c, the consolidation divergence of a and c can actually be regarded as the central oscillation of B. Although B has not appeared when a exists, it may as well be viewed in this way.