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      <text>23.1.2.4 Harmonics</text>
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      <text><![CDATA[<h4>Harmonics</h4>
In representing a non-sinusoidal function of period \(2\pi\) by a Fourier series we shall see shortly that
only certain sinusoids will be required:
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(a) \( A_1 \cos t \) (and \( B_1 \sin t \) )
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These also have period \(2\pi\) and together are referred to as the <b>first harmonic</b> (or <b>fundamental harmonic</b>).
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(b) \( A_2 \cos 2t \) (and \( B_2 \sin 2t \) )
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These have half the period, and double the frequency, of the first harmonic and are referred to as the <b>second harmonic</b>.
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(c) \( A_3 \cos 3t \) (and \( B_3 \sin 3t \) )
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These have period \( \dfrac{2\pi}{3}\) and constitute the <b>third harmonic</b>.
<p></p><p></p>
In general the Fourier series of a function of period \(2\pi\) will require harmonics of the type
\[ A_n \cos nt \hspace{1cm} ( \text{and}&nbsp;\hspace{0.3cm} &nbsp;B_n \sin nt)\]
 where \( n = 1, 2, 3 \dots \).]]></text>
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