for D being non empty set
for a, b, c, d being Element of D holds
( ((a,b) ][ (c,d)) * (1,1) = a & ((a,b) ][ (c,d)) * (1,2) = b & ((a,b) ][ (c,d)) * (2,1) = c & ((a,b) ][ (c,d)) * (2,2) = d )