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Integer Laws

Same laws that also hold in N.

Proposition:

forall x in Z, y in Z: x+y = y+x.

Proof: Take arbitrary x in Z,y in Z. We have

x+y = (definition of +)
I(x0 +N y0, x1 +N y1) = (commutativity of +N)
I(y0 +N x0, y1 +N x1) = (definition of +)
y+x.

Author: Wolfgang Schreiner
Last Modification: November 16, 1999

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