A function, continuous in a finite close interval, can be approximated with a preassigned accuracy by Polynomials. A function of a Real variable which is continuous and has period can be approximated by trigonometric Polynomials.

**References**

Szegö, G. *Orthogonal Polynomials, 4th ed.* Providence, RI: Amer. Math. Soc., p. 5, 1975.

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1999-05-26