let x1, x2, x3, y1, y3 be object ; [:{x1,y1},{x2},{x3,y3}:] = {[x1,x2,x3],[y1,x2,x3],[x1,x2,y3],[y1,x2,y3]}
thus [:{x1,y1},{x2},{x3,y3}:] =
[:[:{x1,y1},{x2}:],{x3,y3}:]
by ZFMISC_1:def 3
.=
[:{[x1,x2],[y1,x2]},{x3,y3}:]
by ZFMISC_1:30
.=
{[[x1,x2],x3],[[x1,x2],y3],[[y1,x2],x3],[[y1,x2],y3]}
by Th17
.=
{[x1,x2,x3],[y1,x2,x3],[x1,x2,y3],[y1,x2,y3]}
by ENUMSET1:62
; verum