One plus one

The formula that appears on the homepage is a mathematical proposition, more commonly known as 1+1=2 in the special case of integer arithmetic. The unusual notation is from “Principia Mathematica” and so are the following excerpts.

 

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Proof that 1 + 1 = 2. An “occasionally useful proposition”.

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The proof is taken from Principia Mathematica. It appears in the second volume, after all the necessary mathematical machinery has been set up.

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An announcement of the proof appears in the first volume.

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