Volume 33 • Number 3 • 2010   • Rational Recursive Equations Characterizing Cotangent-tangent and Hyperbolic Cotangent-tangent Functions Charinthip Hengkrawit, Vichian Laohakosol and Patanee Udomkavanich Abstract. Using a technique of Rhouma in 2005, closed form solutions of certain rational recursive equations characterizing the cotangent-tangent and the hyperbolic cotangent-tangent function solutions are derived. 2010 Mathematics Subject Classification: 39B32. Full text: PDF