let RNS1, RNS2 be RealLinearSpace; :: thesis: ( RLSStruct(# the carrier of RNS1, the ZeroF of RNS1, the addF of RNS1, the Mult of RNS1 #) = RLSStruct(# the carrier of RNS2, the ZeroF of RNS2, the addF of RNS2, the Mult of RNS2 #) implies for X being set holds
( X is Basis of RNS1 iff X is Basis of RNS2 ) )

assume A1: RLSStruct(# the carrier of RNS1, the ZeroF of RNS1, the addF of RNS1, the Mult of RNS1 #) = RLSStruct(# the carrier of RNS2, the ZeroF of RNS2, the addF of RNS2, the Mult of RNS2 #) ; :: thesis: for X being set holds
( X is Basis of RNS1 iff X is Basis of RNS2 )

let X be set ; :: thesis: ( X is Basis of RNS1 iff X is Basis of RNS2 )
set V = RNS1;
set W = RNS2;
hereby :: thesis: ( X is Basis of RNS2 implies X is Basis of RNS1 )
assume X is Basis of RNS1 ; :: thesis: X is Basis of RNS2
then reconsider A = X as Basis of RNS1 ;
reconsider B = A as Subset of RNS2 by A1;
( A is linearly-independent & Lin A = RLSStruct(# the carrier of RNS1, the ZeroF of RNS1, the addF of RNS1, the Mult of RNS1 #) ) by RLVECT_3:def 3;
then A3: B is linearly-independent by A1, Th17;
set W0 = (Omega). RNS2;
A4: (Omega). RNS2 = RLSStruct(# the carrier of RNS2, the ZeroF of RNS2, the addF of RNS2, the Mult of RNS2 #) by RLSUB_1:def 4;
A5: Lin B is strict Subspace of (Omega). RNS2 by REAL_NS2:49;
A6: [#] (Lin A) = the carrier of RNS2 by A1, RLVECT_3:def 3;
the carrier of (Lin B) = [#] (Lin B)
.= the carrier of ((Omega). RNS2) by Th16, A1, A6, A4 ;
then Lin B = (Omega). RNS2 by A5, RLSUB_1:32
.= RLSStruct(# the carrier of RNS2, the ZeroF of RNS2, the addF of RNS2, the Mult of RNS2 #) by RLSUB_1:def 4 ;
hence X is Basis of RNS2 by A3, RLVECT_3:def 3; :: thesis: verum
end;
assume X is Basis of RNS2 ; :: thesis: X is Basis of RNS1
then reconsider A = X as Basis of RNS2 ;
reconsider B = A as Subset of RNS1 by A1;
( A is linearly-independent & Lin A = RLSStruct(# the carrier of RNS2, the ZeroF of RNS2, the addF of RNS2, the Mult of RNS2 #) ) by RLVECT_3:def 3;
then A8: B is linearly-independent by A1, Th17;
set V0 = (Omega). RNS1;
A9: (Omega). RNS1 = RLSStruct(# the carrier of RNS1, the ZeroF of RNS1, the addF of RNS1, the Mult of RNS1 #) by RLSUB_1:def 4;
A10: Lin B is strict Subspace of (Omega). RNS1 by REAL_NS2:49;
A11: [#] (Lin A) = the carrier of RNS1 by A1, RLVECT_3:def 3;
the carrier of (Lin B) = [#] (Lin B)
.= the carrier of ((Omega). RNS1) by A9, Th16, A11, A1 ;
then Lin B = (Omega). RNS1 by A10, RLSUB_1:32
.= RLSStruct(# the carrier of RNS1, the ZeroF of RNS1, the addF of RNS1, the Mult of RNS1 #) by RLSUB_1:def 4 ;
hence X is Basis of RNS1 by A8, RLVECT_3:def 3; :: thesis: verum