theorem :: REWRITE3:41

for x, y1, y2, z being object
for E being non empty set
for F being Subset of (E ^omega)
for TS being non empty transition-system over F st the Tran of TS is Function & [x,[y1,z]] in ==>.-relation TS & [x,[y2,z]] in ==>.-relation TS holds
y1 = y2