Complex numbers/Field/Fact/Proof
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Proof
The field properties for the addition are clear, since the corresponding properties hold for . We have
so is the neutral element for the multiplication. The commutativity of the multiplication follows directly from its formula. To show associativity of the multiplication we compute
We also get
Suppose now that
Then at least one of the numbers or is different from and therefore . Hence is a complex number and
so every element has an inverse with respect to the multiplication. The distributivity law follows from