On the Cosine Functional Equation

  • Pl. Kannappan


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
$$f\left (x + y\right) + f\left (x - y\right ) = 2f(x)f(y)$$


Abelian Group Functional Equation Continuous Solution Functional Inequality Real Character 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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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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