Proof
(related to Proposition: Algebraic Structure of Complex Numbers Together with Addition)
The set of complex numbers \(\mathbb C\), together with the specific addition operation "\(+\)" is a commutative group, because:
 The addition operation is associative, i.e. \((x+y)+z=x+(y+z)\) is valid for all \(x,y,z\in\mathbb C\).
 We have shown the existence of a neutral element of addition  the number \(0\in\mathbb C\), i.e. such that \(0+x=x+0=x\) for all \(x\in\mathbb C\).
 For every \(x\in\mathbb C\), there there exists an inverse complex number \(x\in\mathbb C\), such that \(x+(x)=0\).
 For every \(x\in\mathbb C\), there there exists an inverse complex number \(x\in\mathbb C\), such that \(x+(x)=0\).
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References
Bibliography
 Forster Otto: "Analysis 1, Differential und Integralrechnung einer VerĂ¤nderlichen", Vieweg Studium, 1983