let a, b be positive Real; :: thesis: ( a < b implies not seq_a^ b,1,0 in Big_Oh (seq_a^ a,1,0 ) )
assume A1:
a < b
; :: thesis: not seq_a^ b,1,0 in Big_Oh (seq_a^ a,1,0 )
set f = seq_a^ b,1,0 ;
set g = seq_a^ a,1,0 ;
hereby :: thesis: verum
assume
seq_a^ b,1,
0 in Big_Oh (seq_a^ a,1,0 )
;
:: thesis: contradictionthen consider s being
Element of
Funcs NAT ,
REAL such that A2:
s = seq_a^ b,1,
0
and A3:
ex
c being
Real ex
N being
Element of
NAT st
(
c > 0 & ( for
n being
Element of
NAT st
n >= N holds
(
s . n <= c * ((seq_a^ a,1,0 ) . n) &
s . n >= 0 ) ) )
;
consider c being
Real,
N being
Element of
NAT such that A4:
c > 0
and A5:
for
n being
Element of
NAT st
n >= N holds
(
s . n <= c * ((seq_a^ a,1,0 ) . n) &
s . n >= 0 )
by A3;
set d =
(log 2,b) - (log 2,a);
log 2,
b > (log 2,a) + 0
by A1, POWER:65;
then A6:
(log 2,b) - (log 2,a) > 0
by XREAL_1:22;
set N0 =
[/((log 2,c) / ((log 2,b) - (log 2,a)))\];
set N1 =
max N,
[/((log 2,c) / ((log 2,b) - (log 2,a)))\];
A7:
(
max N,
[/((log 2,c) / ((log 2,b) - (log 2,a)))\] >= N &
max N,
[/((log 2,c) / ((log 2,b) - (log 2,a)))\] >= [/((log 2,c) / ((log 2,b) - (log 2,a)))\] )
by XXREAL_0:25;
(
max N,
[/((log 2,c) / ((log 2,b) - (log 2,a)))\] = N or
max N,
[/((log 2,c) / ((log 2,b) - (log 2,a)))\] = [/((log 2,c) / ((log 2,b) - (log 2,a)))\] )
by XXREAL_0:16;
then reconsider N1 =
max N,
[/((log 2,c) / ((log 2,b) - (log 2,a)))\] as
Element of
NAT by A7, INT_1:16;
set n =
N1 + 1;
set e = 2
to_power ((N1 + 1) * (log 2,a));
A8:
2
to_power ((N1 + 1) * (log 2,a)) > 0
by POWER:39;
N1 + 1
> N1 + 0
by XREAL_1:10;
then A9:
(
N1 + 1
> N &
N1 + 1
> [/((log 2,c) / ((log 2,b) - (log 2,a)))\] )
by A7, XXREAL_0:2;
[/((log 2,c) / ((log 2,b) - (log 2,a)))\] >= (log 2,c) / ((log 2,b) - (log 2,a))
by INT_1:def 5;
then
N1 + 1
> (log 2,c) / ((log 2,b) - (log 2,a))
by A9, XXREAL_0:2;
then
(N1 + 1) * ((log 2,b) - (log 2,a)) > ((log 2,c) / ((log 2,b) - (log 2,a))) * ((log 2,b) - (log 2,a))
by A6, XREAL_1:70;
then
(N1 + 1) * ((log 2,b) - (log 2,a)) > log 2,
c
by A6, XCMPLX_1:88;
then
2
to_power ((N1 + 1) * ((log 2,b) - (log 2,a))) > 2
to_power (log 2,c)
by POWER:44;
then
2
to_power (((N1 + 1) * (log 2,b)) - ((N1 + 1) * (log 2,a))) > c
by A4, POWER:def 3;
then
(2 to_power ((N1 + 1) * (log 2,b))) / (2 to_power ((N1 + 1) * (log 2,a))) > c
by POWER:34;
then
((2 to_power ((N1 + 1) * (log 2,b))) / (2 to_power ((N1 + 1) * (log 2,a)))) * (2 to_power ((N1 + 1) * (log 2,a))) > c * (2 to_power ((N1 + 1) * (log 2,a)))
by A8, XREAL_1:70;
then
2
to_power ((N1 + 1) * (log 2,b)) > c * (2 to_power ((N1 + 1) * (log 2,a)))
by A8, XCMPLX_1:88;
then
b to_power (N1 + 1) > c * (2 to_power ((N1 + 1) * (log 2,a)))
by Lm3;
then A10:
b to_power (N1 + 1) > c * (a to_power (N1 + 1))
by Lm3;
(seq_a^ b,1,0 ) . (N1 + 1) <= c * ((seq_a^ a,1,0 ) . (N1 + 1))
by A2, A5, A9;
then
b to_power ((1 * (N1 + 1)) + 0 ) <= c * ((seq_a^ a,1,0 ) . (N1 + 1))
by Def1;
hence
contradiction
by A10, Def1;
:: thesis: verum
end;