
theorem Th2:
  for X be non empty set, S be SigmaField of X, M be sigma_Measure
  of S, f be PartFunc of X,REAL, E be Element of S, a be Real st f
is_integrable_on M & E c= dom f & M.E < +infty & (for x be Element of X st x in
  E holds a <= f.x) holds (a qua ExtReal)*M.E <= Integral(M,f|E)
by Th1;
