The Trigonometric Fourier Series
In the previous chapter we obtained a set of formulas that we suspect will allow us to describe any “reasonable” periodic function as a (possibly infinite) linear combination of sines and cosines. Let us now see about actually computing with these formulas.
First, though, a little terminology and notation so that we can conveniently refer to this important set of formulas.
9.1 Defining the Trigonometric Fourier Series
Terminology and Notation
Let f be a periodic function with period p where p is some positive number. The (trigonometric) Fourier series for f is the infinite series
where, for k = 1, 2, 3, …,
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