let x1, x2, y1, y2 be object ; for E being non empty set
for F being Subset of (E ^omega)
for TS being non empty transition-system over F st x1,x2 ==>. y1,y2,TS holds
==>.-relation TS reduces [x1,x2],[y1,y2]
let E be non empty set ; for F being Subset of (E ^omega)
for TS being non empty transition-system over F st x1,x2 ==>. y1,y2,TS holds
==>.-relation TS reduces [x1,x2],[y1,y2]
let F be Subset of (E ^omega); for TS being non empty transition-system over F st x1,x2 ==>. y1,y2,TS holds
==>.-relation TS reduces [x1,x2],[y1,y2]
let TS be non empty transition-system over F; ( x1,x2 ==>. y1,y2,TS implies ==>.-relation TS reduces [x1,x2],[y1,y2] )
assume
x1,x2 ==>. y1,y2,TS
; ==>.-relation TS reduces [x1,x2],[y1,y2]
then
[[x1,x2],[y1,y2]] in ==>.-relation TS
by Def4;
hence
==>.-relation TS reduces [x1,x2],[y1,y2]
by REWRITE1:15; verum