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      <text>23.2 Introduction</text>
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      <text><![CDATA[<h4>Introduction</h4>
In this Section we show how a periodic function can be expressed as a series of sines and cosines.
We begin by obtaining some standard integrals involving sinusoids. We then <b>assume</b> that if \(f(t)\) is
a periodic function, of period \(2\pi\), then the Fourier series expansion takes the form:
\[ f(t) = \dfrac{a_0}{2} + \sum _{n=1}^\infty \left( a_n \cos nt + b_n \sin nt \right) .\]
Our main purpose here is to show how the constants in this expansion, \(a_n\) (for \(n = 0, 1, 2, 3 \dots \) ) and \(b_n\) (for \(n = 1, 2, 3, \dots\) ), may be determined for any given function \(f(t)\).]]></text>
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