let a, b be Element of ExWALattice; :: thesis: ( a = 1 & b = 3 implies a "/\" b = 3 )
reconsider aa = a, bb = b as Element of {0,1,2,3,4} ;
assume A1: ( a = 1 & b = 3 ) ; :: thesis: a "/\" b = 3
a "/\" b = aa ex1234"/\" bb by EXNDef
.= bb by A1, ExMeetDef ;
hence a "/\" b = 3 by A1; :: thesis: verum