2013年11月20日 · I would very much say that 1+1 = 2 is true by definition, it's a bit like the statement "the standard metre is one metre long" before the redefinition in terms of light speed. Your sceptic must understand what the symbols 1+1 means otherwise he is not justified in claiming that 1+1 is two.

2014年5月16日 · Is 1+1=2? You would think so! What if I was to tell you that I could prove that 1 + 1 is actually equal to 1. Read on, and I'll explain!

2013年1月15日 · The work of G. Peano shows that it's not hard to produce a useful set of axioms that can prove 1+1=2 much more easily than Whitehead and Russell do. The later theorem alluded to, that $1+1=2$, appears in section $\ast110$:

2022年7月12日 · Some people think that 1=2, and the math actually makes sense. But can you prove them wrong and find the flaw in their logic?

Other than that, it's simple ideas we all know are true, but if you think about it, these are the only things you need to know to prove 1+1=2.

2018年5月28日 · The symbol "1" would normally be defined as the multiplicative identity, and "2" would normally be defined as the sum of the multiplicative identity with itself. That 1+1=2 wouldn't be an "axiom", but would rather be implied rather directly by those definitions.

If you define $2$ to be an abbreviation for $1+1$, assuming we know what $+$ is, then $1+1=2$ is certainly a theorem, with a very short proof. However, a more refined possibility is to define the natural numbers as certain sets, and then define the plus operation by induction.

2023年11月3日 · It is common knowledge that adding one and one equals two, mathematically, 1+1=2. I believe that in a theoretical sense, this is true. It has been, and as long as traditional arithmetics...

2007年8月2日 · So then it is easy to show that 1+1=2 as follows. 1+1=a+S (0)=S (0+1)=S (1)=2. But then one might worry about the successor relation. It might seem as though we have simply assumed addition in the definition of the successor relation (i.e. it …

2017年7月19日 · A logical truth would be something like $1+1=1+1$ or $2=2$, because the $=$ is a logical symbol, and its meaning is fixed (and is exactly what you think it is) And yes, $1+1=2$ could be a logical consequence of some axioms involving numbers.