The Irminones was an early Germanic proto-tribe, or cultural group. They dwelt in eastern Germany, roughly between the Elbe and Oder Rivers some unknown time in the ancient past (perhaps 500 BC or 1000 BC), until the differentiation of localized Teutonic tribes (Lombards, Marcomanni, Quadi) in that region circa 10 CE.
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The formula and its proof remain correct if the coefficients a, b and c are complex numbers, or more generally members of any field whose characteristic is not 2. ...