A survey for generalized trigonometric and hyperbolic functions

Abstract

The generalized trigonometric functions which have a short history, were introduced by Lindqvist two decades ago. Since 2012, many mathematician began to study their classical inequalities, general convexity and concavity, multiple-angle formulas and parameter convexity and concavity. A number of results have been obtained. This is a survey. Some new refinements, generalizations, applications, and related problems are summarized.