abstract: The discriminantal arrangement is defined by Manin-Schechtman in 1989 as a generalization of braid arrangement. The combinatorics (i.e., intersection lattice) of the discriminantal arrangement is not well-known. In my talking I will explain connection between combinatorics of discriminantal arrangement in codimension 2 and quadrics in Grassmannain. In particular this connection leads to an alternative statement and proof of Pappus’s theorem.