for X, Y being set
for h1, h2 being PartFunc of REAL,REAL holds
( ( h1 | X is increasing & h2 | Y is V8() implies (h1 + h2) | (X /\ Y) is increasing ) & ( h1 | X is decreasing & h2 | Y is V8() implies (h1 + h2) | (X /\ Y) is decreasing ) )