let GF be Graph-yielding Function; :: thesis: ( GF is acyclic & GF is connected implies GF is Tree-like )
assume A1: ( GF is acyclic & GF is connected ) ; :: thesis: GF is Tree-like
let x be object ; :: according to GLIB_002:def 14 :: thesis: ( x in dom GF implies ex G being _Graph st
( GF . x = G & G is Tree-like ) )
assume A2: x in dom GF ; :: thesis: ex G being _Graph st
( GF . x = G & G is Tree-like )
then consider G being _Graph such that
A3: ( GF . x = G & G is acyclic ) by A1;
consider G0 being _Graph such that
A4: ( GF . x = G0 & G0 is connected ) by A1, A2;
take G ; :: thesis: ( GF . x = G & G is Tree-like )
thus ( GF . x = G & G is Tree-like ) by A3, A4; :: thesis: verum