let rseq be Real_Sequence; :: thesis: ( ( for n being Nat holds 0 <= rseq . n ) implies ( ( for n being Nat holds 0 <= (Partial_Sums rseq) . n ) & ( for n being Nat holds rseq . n <= (Partial_Sums rseq) . n ) & ( rseq is summable implies ( ( for n being Nat holds (Partial_Sums rseq) . n <= Sum rseq ) & ( for n being Nat holds rseq . n <= Sum rseq ) ) ) ) )
assume A1: for n being Nat holds 0 <= rseq . n ; :: thesis: ( ( for n being Nat holds 0 <= (Partial_Sums rseq) . n ) & ( for n being Nat holds rseq . n <= (Partial_Sums rseq) . n ) & ( rseq is summable implies ( ( for n being Nat holds (Partial_Sums rseq) . n <= Sum rseq ) & ( for n being Nat holds rseq . n <= Sum rseq ) ) ) )
A2: Partial_Sums rseq is V50() by ;
thus A3: for n being Nat holds 0 <= (Partial_Sums rseq) . n :: thesis: ( ( for n being Nat holds rseq . n <= (Partial_Sums rseq) . n ) & ( rseq is summable implies ( ( for n being Nat holds (Partial_Sums rseq) . n <= Sum rseq ) & ( for n being Nat holds rseq . n <= Sum rseq ) ) ) )
proof
let n be Nat; :: thesis: 0 <= (Partial_Sums rseq) . n
A4: ( n = n + 0 & (Partial_Sums rseq) . 0 = rseq . 0 ) by SERIES_1:def 1;
0 <= rseq . 0 by A1;
hence 0 <= (Partial_Sums rseq) . n by ; :: thesis: verum
end;
thus A5: for n being Nat holds rseq . n <= (Partial_Sums rseq) . n :: thesis: ( rseq is summable implies ( ( for n being Nat holds (Partial_Sums rseq) . n <= Sum rseq ) & ( for n being Nat holds rseq . n <= Sum rseq ) ) )
proof
let n be Nat; :: thesis: rseq . n <= (Partial_Sums rseq) . n
now :: thesis: ( ( n = 0 & rseq . n <= (Partial_Sums rseq) . n ) or ( n <> 0 & rseq . n <= (Partial_Sums rseq) . n ) )
per cases ( n = 0 or n <> 0 ) ;
case n = 0 ; :: thesis: rseq . n <= (Partial_Sums rseq) . n
end;
case A6: n <> 0 ; :: thesis: rseq . n <= (Partial_Sums rseq) . n
A7: n in NAT by ORDINAL1:def 12;
set nn = n - 1;
0 + 1 <= n by ;
then A8: n - 1 in NAT by ;
then 0 <= (Partial_Sums rseq) . (n - 1) by A3;
then ( (n - 1) + 1 = n & (rseq . n) + 0 <= (rseq . n) + ((Partial_Sums rseq) . (n - 1)) ) by XREAL_1:7;
hence rseq . n <= (Partial_Sums rseq) . n by ; :: thesis: verum
end;
end;
end;
hence rseq . n <= (Partial_Sums rseq) . n ; :: thesis: verum
end;
assume rseq is summable ; :: thesis: ( ( for n being Nat holds (Partial_Sums rseq) . n <= Sum rseq ) & ( for n being Nat holds rseq . n <= Sum rseq ) )
then A9: Partial_Sums rseq is bounded_above by ;
thus A10: for n being Nat holds (Partial_Sums rseq) . n <= Sum rseq :: thesis: for n being Nat holds rseq . n <= Sum rseq
proof
let n be Nat; :: thesis: (Partial_Sums rseq) . n <= Sum rseq
(Partial_Sums rseq) . n <= lim (Partial_Sums rseq) by ;
hence (Partial_Sums rseq) . n <= Sum rseq by SERIES_1:def 3; :: thesis: verum
end;
let n be Nat; :: thesis: rseq . n <= Sum rseq
A11: rseq . n <= (Partial_Sums rseq) . n by A5;
(Partial_Sums rseq) . n <= Sum rseq by A10;
hence rseq . n <= Sum rseq by ; :: thesis: verum