
theorem Th11:
for I,J be Interval holds [:I,J:] is Subset of [:RNS_Real,RNS_Real:]
 & [:I,J:] in sigma measurable_rectangles(L-Field,L-Field)
proof
    let I,J be Interval;
    I in L-Field & J in L-Field by MEASUR10:5,MEASUR12:75; then
A1: [:I,J:] in measurable_rectangles(L-Field,L-Field);
    measurable_rectangles(L-Field,L-Field)
     c= sigma measurable_rectangles(L-Field,L-Field) by PROB_1:def 9;
    hence thesis by A1;
end;
