let S be non empty lower-bounded up-complete Poset; :: thesis: for T being non empty up-complete Poset
for x being Element of [:S,T:] holds proj2 (compactbelow x) = compactbelow (x `2)
let T be non empty up-complete Poset; :: thesis: for x being Element of [:S,T:] holds proj2 (compactbelow x) = compactbelow (x `2)
let x be Element of [:S,T:]; :: thesis: proj2 (compactbelow x) = compactbelow (x `2)
A1: Bottom S <= x `1 by YELLOW_0:44;
thus proj2 (compactbelow x) c= compactbelow (x `2) by Th51; :: according to XBOOLE_0:def 10 :: thesis: compactbelow (x `2) c= proj2 (compactbelow x)
let a be object ; :: according to TARSKI:def 3 :: thesis: ( not a in compactbelow (x `2) or a in proj2 (compactbelow x) )
assume A2: a in compactbelow (x `2) ; :: thesis: a in proj2 (compactbelow x)
then reconsider a9 = a as Element of T ;
a9 <= x `2 by A2, WAYBEL_8:4;
then A3: [(Bottom S),a9] <= [(x `1),(x `2)] by A1, YELLOW_3:11;
the carrier of [:S,T:] = [: the carrier of S, the carrier of T:] by YELLOW_3:def 2;
then A4: x = [(x `1),(x `2)] by MCART_1:21;
A5: ( [(Bottom S),a9] `1 = Bottom S & [(Bottom S),a9] `2 = a9 ) ;
a9 is compact by A2, WAYBEL_8:4;
then [(Bottom S),a9] is compact by A5, Th23, WAYBEL_3:15;
then [(Bottom S),a9] in compactbelow [(x `1),(x `2)] by A3;
hence a in proj2 (compactbelow x) by A4, XTUPLE_0:def 13; :: thesis: verum