References
- Calcut., J. S. (2006). Rationality and the tangent function. Preprint. https://www2.oberlin.edu/faculty/jcalcut/tanpap.pdf
- Jahnel, J. (2010). When is the (co)sine of a rational angle equal to a rational number? arXiv:1006.2938.
- Lehmer, D. H. (1933). A note on trigonometric algebraic numbers. The American Mathematical Monthly, 40(3), 165–166. https://doi.org/10.2307/2301023
- Nelson, R. B. (2018). Further integral skinning with applications. The College Mathematics Journal, 49(5), 327–332. https://doi.org/10.1080/07468342.2018.1507383
- Niven, I. (1956). Irrational numbers. The Carus Mathematical Monographs, No. 11. The Mathematical Association of America. Distributed by John Wiley and Sons, Inc.
- Paolillo, B., & Vincenzi, G. (2021a). On the rational values of trigonometric functions of angles that are rational in degrees. Mathematics Magazine, 94(2), 132–134. https://doi.org/10.1080/0025570X.2021.1869479
- Paolillo, B., & Vincenzi, G. (2021b). An elementary proof of Niven's theorem via the tangent function. International Journal of Mathematical Education in Science and Technology, 52(6), 959–964. https://doi.org/10.1080/0020739X.2020.1799088
- Tangsupphathawat, P. (2014). Algebraic trigonometric values at rational multipliers of π. Acta et Commentationes Universitatis Tartuensis de Mathematica, 18(1), 9–18. https://doi.org/10.12697/ACUTM.2014.18.02