theorem Th6: :: INTEGR15:6

for A being non empty closed_interval Subset of REAL
for f being Function of A,REAL
for T being DivSequence of A
for S being middle_volume_Sequence of f,T
for i being Element of NAT st f | A is bounded_above holds
(middle_sum (f,S)) . i <= (upper_sum (f,T)) . i