let x, y, z be set ; :: thesis: InnerVertices (BitGFA3Str (x,y,z)) is Relation
set S1 = GFA3AdderStr (x,y,z);
set S2 = GFA3CarryStr (x,y,z);
( InnerVertices (GFA3AdderStr (x,y,z)) is Relation & InnerVertices (GFA3CarryStr (x,y,z)) is Relation ) by Th107, FACIRC_1:58;
hence InnerVertices (BitGFA3Str (x,y,z)) is Relation by FACIRC_1:3; :: thesis: verum