Pentagon relation and Biedenharn-Elliott identity

The main subject of the paper is the pentagon relation. This relation can be expressed in different ways. We start with the natural geometric form of the pentagon relation. Then we express it in algebraic form as a family of equations with a set of linear maps as variables. Next, we derive several equivalent forms of the algebraic pentagon relation. These forms can be expressed using the classical notion of 6j-symbols. Finally, we show how to extract a solution of the pentagon relation from any modular category.