Argand's "Reflexions" of 1815 -- An English Translation

Abstract

This is a translation from French into English of Argand's "Reflexions sur la nouvelle théorie des imaginaires, suivies d'une application à la démonstration d'un théorème d'analise", published in 1815. Argand reprises the method of representing complex numbers as points in the plane, which he first introduced in 1806. He takes up complex addition, multiplication, division, root taking, and absolute value. He gives an early and perhaps the first valid proof of the fundamental theorem of algebra, assuming only that the absolute value of a polynomial with complex coefficients assumes an absolute minimum in the complex plane. Argand's proof is simple and direct, variants of it being reproduced by Cauchy and textbook writers throughout the nineteenth century.