Adding Some Perspective to de Moivre's Theorem: Visualising the "n"-th Roots of Unity

Autor/in	Bardell, Nicholas S.
Titel	Adding Some Perspective to de Moivre's Theorem: Visualising the "n"-th Roots of Unity
Quelle	In: Australian Senior Mathematics Journal, 29 (2015) 2, S.40-50 (11 Seiten) PDF als Volltext Verfügbarkeit
Sprache	englisch
Dokumenttyp	gedruckt; online; Zeitschriftenaufsatz
ISSN	0819-4564
Schlagwörter	Mathematics; Equations (Mathematics); Numbers; Algebra; Mathematical Formulas; Foreign Countries; Problem Solving; Mathematical Concepts; Teaching Methods; Fractions; Mathematics Instruction; Australia + Suchen Sie Ihr Suchwort? Mathematik; Equations; Mathematics; Gleichungslehre; Zahlenraum; Mathematische Formel; Ausland; Problemlösen; Teaching method; Lehrmethode; Unterrichtsmethode; Bruchrechnung; Mathematics lessons; Mathematikunterricht; Australien
Abstract	Traditionally, "z" is assumed to be a complex number and the roots are usually determined by using de Moivre's theorem adapted for fractional indices. The roots are represented in the Argand plane by points that lie equally pitched around a circle of unit radius. The "n"-th roots of unity always include the real number 1, and also include the real number -1 if "n" is even. The non-real "n"-th roots of unity always form complex conjugate pairs. This topic is taught to students studying a mathematics specialism (ACARA, n.d., Unit 3, Topic 1: Complex Numbers) as an application of de Moivre's theorem with the understanding that the roots occur in the complex domain. Meanwhile, in the Cartesian plane, a closely related topic deals with the solution of polynomials (ACARA, n.d., Unit 2, Topic 3: Real and Complex Numbers). The aim of this paper is to demonstrate visually the connection between the reduced polynomial "y" = "x"[superscript "n"] - 1 in the Cartesian plane and the resulting n-roots which invariably appear in the Argand plane. There is no contradiction here: the reader will find a three-dimensional surface representation of Equation (2) provides the full link between both the Cartesian and Argand planes, and illustrates not only the location of the roots in relation to the original equation but also shows why they occur with conjugate pairings. Examples will be provided for the cases "n" = 3, "n" = 5 and "n" = 8 which will be sufficient to illustrate the general pattern that emerges. The approach adopted here is a natural extension of the surface visualisation techniques first presented by Bardell (2012) for quadratic equations. (ERIC).
Anmerkungen	Australian Association of Mathematics Teachers (AAMT). GPO Box 1729, Adelaide 5001, South Australia. Tel: +61-8-8363-0288; Fax: +61-8-8362-9288; e-mail: office@aamt.edu.au; Web site: http://www.aamt.edu.au
Erfasst von	ERIC (Education Resources Information Center), Washington, DC
Update	2021/2/06