reserve Omega, Omega1, Omega2 for non empty set;
reserve Sigma for SigmaField of Omega;
reserve S1 for SigmaField of Omega1;
reserve S2 for SigmaField of Omega2;
reserve F for random_variable of S1,S2;

theorem Th15:
  for F be Function of Omega1, Omega2
  holds F is random_variable of
  Trivial-SigmaField Omega1, Trivial-SigmaField Omega2
  proof
    let F be Function of Omega1, Omega2;
    set S1 = Trivial-SigmaField Omega1;
    set S2 = Trivial-SigmaField Omega2;
    for y being set st y in S2 holds F"y in S1;
    hence thesis by FINANCE1:def 5;
  end;
