The th Roots of Unity are Roots
of the Cyclotomic Equation
See also Cyclotomic Equation, de Moivre's Identity, de Moivre Number, Unity
Courant, R. and Robbins, H. ``De Moivre's Formula and the Roots of Unity.'' §5.3 in
What is Mathematics?: An Elementary Approach to Ideas and Methods, 2nd ed.
Oxford, England: Oxford University Press, pp. 98-100, 1996.