let G be _finite Tree-like _Graph; :: thesis: ex p being non empty Graph-yielding _finite Tree-like FinSequence st
( p . 1 is _trivial & p . 1 is edgeless & p . (len p) = G & len p = G .order() & ( for n being Element of dom p st n <= (len p) - 1 holds
ex v1, v2 being Vertex of G ex e being object st
( p . (n + 1) is addAdjVertex of p . n,v1,e,v2 & e in (the_Edges_of G) \ (the_Edges_of (p . n)) & ( ( v1 in the_Vertices_of (p . n) & not v2 in the_Vertices_of (p . n) ) or ( not v1 in the_Vertices_of (p . n) & v2 in the_Vertices_of (p . n) ) ) ) ) )
set H = the _trivial Subgraph of G;
consider p being non empty Graph-yielding _finite Tree-like FinSequence such that
A1: ( p . 1 == the _trivial Subgraph of G & p . (len p) = G & len p = ((G .order()) - ( the _trivial Subgraph of G .order())) + 1 ) and
A2: for n being Element of dom p st n <= (len p) - 1 holds
ex v1, v2 being Vertex of G ex e being object st
( p . (n + 1) is addAdjVertex of p . n,v1,e,v2 & e in (the_Edges_of G) \ (the_Edges_of (p . n)) & ( ( v1 in the_Vertices_of (p . n) & not v2 in the_Vertices_of (p . n) ) or ( not v1 in the_Vertices_of (p . n) & v2 in the_Vertices_of (p . n) ) ) ) by Th71;
take p ; :: thesis: ( p . 1 is _trivial & p . 1 is edgeless & p . (len p) = G & len p = G .order() & ( for n being Element of dom p st n <= (len p) - 1 holds
ex v1, v2 being Vertex of G ex e being object st
( p . (n + 1) is addAdjVertex of p . n,v1,e,v2 & e in (the_Edges_of G) \ (the_Edges_of (p . n)) & ( ( v1 in the_Vertices_of (p . n) & not v2 in the_Vertices_of (p . n) ) or ( not v1 in the_Vertices_of (p . n) & v2 in the_Vertices_of (p . n) ) ) ) ) )
thus ( p . 1 is _trivial & p . 1 is edgeless ) by A1, Th52, GLIB_000:89; :: thesis: ( p . (len p) = G & len p = G .order() & ( for n being Element of dom p st n <= (len p) - 1 holds
ex v1, v2 being Vertex of G ex e being object st
( p . (n + 1) is addAdjVertex of p . n,v1,e,v2 & e in (the_Edges_of G) \ (the_Edges_of (p . n)) & ( ( v1 in the_Vertices_of (p . n) & not v2 in the_Vertices_of (p . n) ) or ( not v1 in the_Vertices_of (p . n) & v2 in the_Vertices_of (p . n) ) ) ) ) )
thus p . (len p) = G by A1; :: thesis: ( len p = G .order() & ( for n being Element of dom p st n <= (len p) - 1 holds
ex v1, v2 being Vertex of G ex e being object st
( p . (n + 1) is addAdjVertex of p . n,v1,e,v2 & e in (the_Edges_of G) \ (the_Edges_of (p . n)) & ( ( v1 in the_Vertices_of (p . n) & not v2 in the_Vertices_of (p . n) ) or ( not v1 in the_Vertices_of (p . n) & v2 in the_Vertices_of (p . n) ) ) ) ) )
thus len p = ((G .order()) - 1) + 1 by A1, GLIB_000:26
.= G .order() ; :: thesis: for n being Element of dom p st n <= (len p) - 1 holds
ex v1, v2 being Vertex of G ex e being object st
( p . (n + 1) is addAdjVertex of p . n,v1,e,v2 & e in (the_Edges_of G) \ (the_Edges_of (p . n)) & ( ( v1 in the_Vertices_of (p . n) & not v2 in the_Vertices_of (p . n) ) or ( not v1 in the_Vertices_of (p . n) & v2 in the_Vertices_of (p . n) ) ) )
thus for n being Element of dom p st n <= (len p) - 1 holds
ex v1, v2 being Vertex of G ex e being object st
( p . (n + 1) is addAdjVertex of p . n,v1,e,v2 & e in (the_Edges_of G) \ (the_Edges_of (p . n)) & ( ( v1 in the_Vertices_of (p . n) & not v2 in the_Vertices_of (p . n) ) or ( not v1 in the_Vertices_of (p . n) & v2 in the_Vertices_of (p . n) ) ) ) by A2; :: thesis: verum