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      <text>16.6.1.3 Simple trigonometric integrals key point</text>
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      <text><![CDATA[<p>The basic rules from which these results can be derived are summarised here:</p>

<div class="HELM_keypoint">
    <h4>Key Point</h4>
    <p>\({\displaystyle\int \sin (kx) \,\mathrm{d}x} = -\dfrac{\cos (kx)}{k} + c\)</p>
    <p>\({\displaystyle\int \cos (kx) \,\mathrm{d}x} = \dfrac{\sin (kx)}{k} + c\)</p>
</div>
<p></p><br>
<p></p>
<p>In engineering applications it is often necessary to integrate functions involving powers of the trigonometric functions such as \({\displaystyle\int \sin^2x \,\mathrm{d}x}\) or \({\displaystyle\int \cos^2\omega t \,\mathrm{d}t}\). Note that these integrals
    cannot be obtained directly from the formulas in the Key Point above. However, by making use of trigonometric identities, the integrands can be re-written in an alternative form. It is often not clear which identities are useful and each case needs
    to be considered individually. Experience and practice are essential. Work through the following question.</p>]]></text>
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