let G1 be _Graph; :: thesis: for G2 being DSimpleGraph of G1 holds
( G1 is chordal iff G2 is chordal )
let G2 be DSimpleGraph of G1; :: thesis: ( G1 is chordal iff G2 is chordal )
consider H being removeDParallelEdges of G1 such that
A1: G2 is removeLoops of H by Th120;
( H is chordal iff G2 is chordal ) by A1, Th65;
hence ( G1 is chordal iff G2 is chordal ) by Th107; :: thesis: verum