A New Approach to Rational Values of Trigonometric Functions
Abstract
It is well known that sin(a\pi/b), cos(a\pi/b), etc., are only rational numbers for a few select integers a and b. We show that this is equivalent to the fact that only for d = 1,2,3,4, and 6 is the primitive dth root of unity of degree 2 over Q.
 Publication:

arXiv eprints
 Pub Date:
 April 2009
 arXiv:
 arXiv:0904.0826
 Bibcode:
 2009arXiv0904.0826D
 Keywords:

 Mathematics  History and Overview;
 Mathematics  Number Theory;
 11R11
 EPrint:
 4 pages, 2 figures, 5 references, with new 6th reference to an easier proof of my result