let L be transitive antisymmetric with_suprema with_infima RelStr ; :: thesis: for a, b, c being Element of L st a <= c holds
a \ b <= c
let a, b, c be Element of L; :: thesis: ( a <= c implies a \ b <= c )
A1: a "/\" ('not' b) <= a by YELLOW_0:23;
assume a <= c ; :: thesis: a \ b <= c
hence a \ b <= c by A1, YELLOW_0:def 2; :: thesis: verum