let x be Element of X; :: thesis: x is DPath of G

x in { W where W is DPath of G : verum } ;

then ex y being DPath of G st y = x ;

hence x is DPath of G ; :: thesis: verum

x in { W where W is DPath of G : verum } ;

then ex y being DPath of G st y = x ;

hence x is DPath of G ; :: thesis: verum