Contracted Bianchi Identity and Angle Relation on n-dimensional Simplicial Complex of Regge Calculus

In this article, we prove the theorems concerning the trace relation of SO(3), SU(2), and SO(n) which are representation of SO(3) and SU(2). An interesting fact we found is the trace relation of SU(2) gives the spherical law of cosine which in turns is a dihedral angle relation, a constraint that must be satisfied by closed Euclidean simplices. Moreover, we applied our results on general group elements to holonomies on the simplicial complex of Regge Calculus, which is the main motivation of this article. Here, we found that: (1) in 4-dimensional Euclidean Regge Gravity, all the holonomy circling a single hinge are simple rotations, and (2) the dihedral angle relation represents the 'contracted' Bianchi identity for a simplicial complex.