2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/60968We solve an elementary extremal problem on trigonometric polynomials and obtain the exact value of the Sidon constant for sets with three elements {n0, n1, n2}: it is \sec(π/ 2n) for n = max(n1-n0, n2-n0, n2-n1) / gcd(n1-n0, n2-n0).7 pagesClassical Analysis and ODEsFunctional Analysis42A05text