let X1, X2, X3, X4, X5, X6, X7, Y1, Y2, Y3, Y4, Y5, Y6, Y7 be set ; ( [:X1,X2,X3,X4,X5,X6,X7:] meets [:Y1,Y2,Y3,Y4,Y5,Y6,Y7:] implies ( X1 meets Y1 & X2 meets Y2 & X3 meets Y3 & X4 meets Y4 & X5 meets Y5 & X6 meets Y6 & X7 meets Y7 ) )
assume A1:
[:X1,X2,X3,X4,X5,X6,X7:] meets [:Y1,Y2,Y3,Y4,Y5,Y6,Y7:]
; ( X1 meets Y1 & X2 meets Y2 & X3 meets Y3 & X4 meets Y4 & X5 meets Y5 & X6 meets Y6 & X7 meets Y7 )
( [:[:[:[:[:[:X1,X2:],X3:],X4:],X5:],X6:],X7:] = [:X1,X2,X3,X4,X5,X6,X7:] & [:[:[:[:[:[:Y1,Y2:],Y3:],Y4:],Y5:],Y6:],Y7:] = [:Y1,Y2,Y3,Y4,Y5,Y6,Y7:] )
by Th85;
then A2:
[:[:[:[:[:X1,X2:],X3:],X4:],X5:],X6:] meets [:[:[:[:[:Y1,Y2:],Y3:],Y4:],Y5:],Y6:]
by A1, ZFMISC_1:104;
then A3:
[:[:[:[:X1,X2:],X3:],X4:],X5:] meets [:[:[:[:Y1,Y2:],Y3:],Y4:],Y5:]
by ZFMISC_1:104;
then A4:
[:[:[:X1,X2:],X3:],X4:] meets [:[:[:Y1,Y2:],Y3:],Y4:]
by ZFMISC_1:104;
then A5:
[:[:X1,X2:],X3:] meets [:[:Y1,Y2:],Y3:]
by ZFMISC_1:104;
then
[:X1,X2:] meets [:Y1,Y2:]
by ZFMISC_1:104;
hence
( X1 meets Y1 & X2 meets Y2 & X3 meets Y3 & X4 meets Y4 & X5 meets Y5 & X6 meets Y6 & X7 meets Y7 )
by A1, A2, A3, A4, A5, ZFMISC_1:104; verum