As claimed by the author, it is the Golden angle Ψ, 137.5°. Examination of the SVG source reveals that the orange angle equals only to 126.27°, with an error of 11° against the claimed value.
<ul><li><a href="//commons.wikimedia.org/wiki/File:Erroneous_golden_angle_pie_chart.png" title="File:Erroneous golden angle pie chart.png">File:Erroneous golden angle pie chart.png</a>: Wolfgang Beyer / *derivative work <a href="//commons.wikimedia.org/wiki/User:Malyszkz" title="User:Malyszkz">Malyszkz</a></li></ul>
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This file was derived from: <a href="//commons.wikimedia.org/wiki/File:Erroneous_golden_angle_pie_chart.png" title="File:Erroneous golden angle pie chart.png">Erroneous golden angle pie chart.png</a>: <a href="//commons.wikimedia.org/wiki/File:Erroneous_golden_angle_pie_chart.png" class="image"><img alt="Erroneous golden angle pie chart.png" src="https://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Erroneous_golden_angle_pie_chart.png/50px-Erroneous_golden_angle_pie_chart.png" decoding="async" width="50" height="49" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Erroneous_golden_angle_pie_chart.png/75px-Erroneous_golden_angle_pie_chart.png 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Erroneous_golden_angle_pie_chart.png/100px-Erroneous_golden_angle_pie_chart.png 2x" data-file-width="230" data-file-height="227"></a><br>