let G1, G2 be _Graph; :: thesis: for e, x, y, X, Y being set st G1 == G2 holds
( ( e Joins x,y,G1 implies e Joins x,y,G2 ) & ( e DJoins x,y,G1 implies e DJoins x,y,G2 ) & ( e SJoins X,Y,G1 implies e SJoins X,Y,G2 ) & ( e DSJoins X,Y,G1 implies e DSJoins X,Y,G2 ) )
let e, x, y, X, Y be set ; :: thesis: ( G1 == G2 implies ( ( e Joins x,y,G1 implies e Joins x,y,G2 ) & ( e DJoins x,y,G1 implies e DJoins x,y,G2 ) & ( e SJoins X,Y,G1 implies e SJoins X,Y,G2 ) & ( e DSJoins X,Y,G1 implies e DSJoins X,Y,G2 ) ) )
assume G1 == G2 ; :: thesis: ( ( e Joins x,y,G1 implies e Joins x,y,G2 ) & ( e DJoins x,y,G1 implies e DJoins x,y,G2 ) & ( e SJoins X,Y,G1 implies e SJoins X,Y,G2 ) & ( e DSJoins X,Y,G1 implies e DSJoins X,Y,G2 ) )
then G1 is Subgraph of G2 by Th90;
hence ( ( e Joins x,y,G1 implies e Joins x,y,G2 ) & ( e DJoins x,y,G1 implies e DJoins x,y,G2 ) & ( e SJoins X,Y,G1 implies e SJoins X,Y,G2 ) & ( e DSJoins X,Y,G1 implies e DSJoins X,Y,G2 ) ) by Th75; :: thesis: verum