theorem Th8: :: YELLOW_7:8

for L being RelStr
for x being Element of L
for X being set holds
( ( x is_<=_than X implies x ~ is_>=_than X ) & ( x ~ is_>=_than X implies x is_<=_than X ) & ( x is_>=_than X implies x ~ is_<=_than X ) & ( x ~ is_<=_than X implies x is_>=_than X ) )