let L be sup-Semilattice; :: thesis: for x being Element of L holds wayabove x is join-closed
let x be Element of L; :: thesis: wayabove x is join-closed

now

let y, z be Element of L; :: thesis: ( y in the carrier of (subrelstr (wayabove x)) & z in the carrier of (subrelstr (wayabove x)) & ex_sup_of {y,z},L implies sup {y,z} in the carrier of (subrelstr (wayabove x)) )
assume that
A1: y in the carrier of (subrelstr (wayabove x)) and
z in the carrier of (subrelstr (wayabove x)) and
ex_sup_of {y,z},L ; :: thesis: sup {y,z} in the carrier of (subrelstr (wayabove x))
y in wayabove x by A1, YELLOW_0:def 15;
then A2: y >> x by WAYBEL_3:8;
y "\/" z >= y by YELLOW_0:22;
then y "\/" z >> x by A2, WAYBEL_3:2;
then y "\/" z in wayabove x by WAYBEL_3:8;
then sup {y,z} in wayabove x by YELLOW_0:41;
hence sup {y,z} in the carrier of (subrelstr (wayabove x)) by YELLOW_0:def 15; :: thesis: verum

end;

then subrelstr (wayabove x) is join-inheriting by YELLOW_0:def 17;
hence wayabove x is join-closed by Def2; :: thesis: verum