set f = { [P1,P2] where P1, P2 is Element of the_sylow_p-subgroups_of_prime p,G : ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
}
;
set E = the_sylow_p-subgroups_of_prime p,G;
A1: now
let x, y1, y2 be set ; :: thesis: ( [x,y1] in { [P1,P2] where P1, P2 is Element of the_sylow_p-subgroups_of_prime p,G : ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
}
& [x,y2] in { [P1,P2] where P1, P2 is Element of the_sylow_p-subgroups_of_prime p,G : ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
}
implies y1 = y2 )

assume [x,y1] in { [P1,P2] where P1, P2 is Element of the_sylow_p-subgroups_of_prime p,G : ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
}
; :: thesis: ( [x,y2] in { [P1,P2] where P1, P2 is Element of the_sylow_p-subgroups_of_prime p,G : ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
}
implies y1 = y2 )

then consider P1', P2' being Element of the_sylow_p-subgroups_of_prime p,G such that
A2: ( [x,y1] = [P1',P2'] & ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1' = H1 & P2' = H2 & h " = g & H2 = H1 |^ g ) ) ;
assume [x,y2] in { [P1,P2] where P1, P2 is Element of the_sylow_p-subgroups_of_prime p,G : ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
}
; :: thesis: y1 = y2
then consider P1'', P2'' being Element of the_sylow_p-subgroups_of_prime p,G such that
A3: ( [x,y2] = [P1'',P2''] & ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1'' = H1 & P2'' = H2 & h " = g & H2 = H1 |^ g ) ) ;
A4: ( x = P1' & y1 = P2' ) by A2, ZFMISC_1:33;
( x = P1'' & y2 = P2'' ) by A3, ZFMISC_1:33;
hence y1 = y2 by A2, A3, A4; :: thesis: verum
end;
now
let x be set ; :: thesis: ( x in { [P1,P2] where P1, P2 is Element of the_sylow_p-subgroups_of_prime p,G : ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
}
implies ex y, z being set st x = [y,z] )

assume x in { [P1,P2] where P1, P2 is Element of the_sylow_p-subgroups_of_prime p,G : ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
}
; :: thesis: ex y, z being set st x = [y,z]
then consider P1, P2 being Element of the_sylow_p-subgroups_of_prime p,G such that
A5: ( x = [P1,P2] & ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g ) ) ;
reconsider y = P1, z = P2 as set ;
take y = y; :: thesis: ex z being set st x = [y,z]
take z = z; :: thesis: x = [y,z]
thus x = [y,z] by A5; :: thesis: verum
end;
then reconsider f = { [P1,P2] where P1, P2 is Element of the_sylow_p-subgroups_of_prime p,G : ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
}
as Function by A1, FUNCT_1:def 1, RELAT_1:def 1;
now
let x be set ; :: thesis: ( ( x in the_sylow_p-subgroups_of_prime p,G implies ex y being set st [x,y] in f ) & ( ex y being set st [x,y] in f implies x in the_sylow_p-subgroups_of_prime p,G ) )
hereby :: thesis: ( ex y being set st [x,y] in f implies x in the_sylow_p-subgroups_of_prime p,G )
assume x in the_sylow_p-subgroups_of_prime p,G ; :: thesis: ex y being set st [x,y] in f
then reconsider P1 = x as Element of the_sylow_p-subgroups_of_prime p,G ;
P1 in the_sylow_p-subgroups_of_prime p,G ;
then consider H1 being Element of Subgroups G such that
A6: ( P1 = H1 & ex P being strict Subgroup of G st
( P = H1 & P is_Sylow_p-subgroup_of_prime p ) ) ;
reconsider H1 = H1 as strict Subgroup of G by A6;
A7: ( H1 is_p-group_of_prime p & not p divides index H1 ) by A6, Def19;
then consider H' being finite Group such that
A8: ( H1 = H' & H' is_p-group_of_prime p ) by Def18;
consider r being natural number such that
A9: card H' = p |^ r by A8, Def17;
reconsider g = h " as Element of G by GROUP_2:51;
set H2 = H1 |^ g;
reconsider H2 = H1 |^ g as strict Subgroup of G ;
A11: card H1 = card H2 by GROUP_3:79;
A12: (card H1) * (index H1) = card G by GROUP_2:177
.= (card H1) * (index H2) by A11, GROUP_2:177 ;
reconsider H'' = H2 as finite Group ;
card H' = card H'' by A8, GROUP_3:79;
then H'' is_p-group_of_prime p by A9, Def17;
then ( H2 is_p-group_of_prime p & not p divides index H2 ) by A7, A12, Def18, XCMPLX_1:5;
then A13: H2 is_Sylow_p-subgroup_of_prime p by Def19;
reconsider H2' = H2 as Element of Subgroups G by GROUP_3:def 1;
H2' in the_sylow_p-subgroups_of_prime p,G by A13;
then reconsider P2 = H2 as Element of the_sylow_p-subgroups_of_prime p,G ;
reconsider y = P2 as set ;
take y = y; :: thesis: [x,y] in f
thus [x,y] in f by A6; :: thesis: verum
end;
given y being set such that A14: [x,y] in f ; :: thesis: x in the_sylow_p-subgroups_of_prime p,G
consider P1, P2 being Element of the_sylow_p-subgroups_of_prime p,G such that
A15: ( [x,y] = [P1,P2] & ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g ) ) by A14;
x = P1 by A15, ZFMISC_1:33;
hence x in the_sylow_p-subgroups_of_prime p,G ; :: thesis: verum
end;
then A16: dom f = the_sylow_p-subgroups_of_prime p,G by RELAT_1:def 4;
now
let y be set ; :: thesis: ( y in rng f implies y in the_sylow_p-subgroups_of_prime p,G )
assume y in rng f ; :: thesis: y in the_sylow_p-subgroups_of_prime p,G
then consider x being set such that
A17: [x,y] in f by RELAT_1:def 5;
consider P1, P2 being Element of the_sylow_p-subgroups_of_prime p,G such that
A18: ( [x,y] = [P1,P2] & ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g ) ) by A17;
y = P2 by A18, ZFMISC_1:33;
hence y in the_sylow_p-subgroups_of_prime p,G ; :: thesis: verum
end;
then rng f c= the_sylow_p-subgroups_of_prime p,G by TARSKI:def 3;
then reconsider f = f as Function of (the_sylow_p-subgroups_of_prime p,G),(the_sylow_p-subgroups_of_prime p,G) by A16, FUNCT_2:4;
take f ; :: thesis: for P1 being Element of the_sylow_p-subgroups_of_prime p,G ex P2 being Element of the_sylow_p-subgroups_of_prime p,G ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P2 = f . P1 & P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )

thus for P1 being Element of the_sylow_p-subgroups_of_prime p,G ex P2 being Element of the_sylow_p-subgroups_of_prime p,G ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P2 = f . P1 & P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g ) :: thesis: verum
proof
let P1 be Element of the_sylow_p-subgroups_of_prime p,G; :: thesis: ex P2 being Element of the_sylow_p-subgroups_of_prime p,G ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P2 = f . P1 & P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )

set P2 = f . P1;
[P1,(f . P1)] in f by A16, FUNCT_1:8;
then consider P1', P2' being Element of the_sylow_p-subgroups_of_prime p,G such that
A19: ( [P1,(f . P1)] = [P1',P2'] & ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P1' = H1 & P2' = H2 & h " = g & H2 = H1 |^ g ) ) ;
consider H1, H2 being strict Subgroup of G, g being Element of G such that
A20: ( P1' = H1 & P2' = H2 & h " = g & H2 = H1 |^ g ) by A19;
reconsider P2 = f . P1 as Element of the_sylow_p-subgroups_of_prime p,G ;
take P2 ; :: thesis: ex H1, H2 being strict Subgroup of G ex g being Element of G st
( P2 = f . P1 & P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )

take H1 ; :: thesis: ex H2 being strict Subgroup of G ex g being Element of G st
( P2 = f . P1 & P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )

take H2 ; :: thesis: ex g being Element of G st
( P2 = f . P1 & P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )

take g ; :: thesis: ( P2 = f . P1 & P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
thus P2 = f . P1 ; :: thesis: ( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g )
thus ( P1 = H1 & P2 = H2 & h " = g & H2 = H1 |^ g ) by A19, A20, ZFMISC_1:33; :: thesis: verum
end;