On the Cosine Functional Equation

  • Pl. Kannappan

Abstract

Application of functional equations has preceded the development of a systematic theory of functional equations. One of the important applications of functional equations is a functional characterization of various functions like Euler’s Γ function, Lebesgue’s singular function, cyclic functions, polynomials, exponential and logarithmic functions, etc. The most extensively studied problem of this sort is that of a functional characterization of the trigonometric functions. One such example is the equation
$$f\left (x + y\right) + f\left (x - y\right ) = 2f(x)f(y)$$

Keywords

Sine 

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Copyright information

© Plenum Press 1968

Authors and Affiliations

  • Pl. Kannappan
    • 1
    • 2
  1. 1.University of WaterlooWaterlooCanada
  2. 2.Annamalai UniversityAnnamalainagarIndia

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