The Golden Ratio — Hidden in Plain Sight
<p>There are many ways to do it, most involving trigonometry with angles of size 36°, 54° or 72°.</p>
<p>One such method is shown below, where I finally fumbled my way to work out an expression for the ratio between the two pentagons’ side lengths: 2tan(54°)cos(54°).</p>
<p>The working shown below is not particularly clear, but don’t worry about the details — it’s not the focus of this article!</p>
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