So would you say that 0.999...(base10) = 0.AAA...(base11) = 0.111...(base2)= 1?
I think I see your first point.
0.A{base11} = 10/11
0.9 = 9/10
0.A - 0.9 = 0.0_09...
0.AA = 10/11 + 10/121
0.99 = 9/10 + 9/100
0.AA - 0.99 = 0.00_1735537190082644628099...
Does this mean that because the difference or "lateness" gets smaller tending to zero each time a single identical digit is added to 0.A and 0.9 respectively, then 0.A... = 0.9...?
(Whereas the difference we get when we do this to say 0.8 and 0.9 gets larger each time so we can't say 0.8... = 0.9...)
0.9{base10}<0.99{base10} but 0.9...{base10}=0.99...{base10}
0.9{base10}<0.A{base11} but 0.9...{base10}=0.A...{base11}
0.8{base10}<0.9{base10} and 0.8...{base10}<0.9...({ase10}
0.9{base10}<0.A{base11} and 0.9...{base10}<0.A...{base11}
I'm not trying to prove "0.999...{base10}=1 "is false, nor that "0.111...(base2)=1" is either - in fact it's an even more fascinating result.
Also "not(not(true))=true" is good enough for me as well.
It's instructive to set out the proof you give for 0.999...=1 in number bases other than ten. For example base eleven, in which the maximum value single digit is conventionally represented as A and amounts to 10 (base ten). 10 (base eleven) amounts to 11 (base ten). So
Let x = 0.AAA...
10x = A.AAA...
10x - x = A
Ax = A
x = 1
0.AAA... = 1
But 0. A (base eleven) = 10/11 (base ten) which is bigger than 0.9 (base ten) = 9/10 (base ten). So shouldn't that inequality apply to 0.AAA... (base eleven) and 0.999... (base ten) as well? (A debatable point maybe...
Still not entirely convinced. If 0.A > 0.9 then surely0.A... > 0.9...?
Or does the fact this is true only when we halt at an equal number of digits after the point make a difference? 0.A = 10/11 and 0.9 = 9/10, so 0.A > 0.9, but 0.A < 0.99.