https://svn.boost.org/trac10/ticket/13603 <blockquote> <p> double sinc1 = 1.0 + x2 * (-1.0 + x2 / 20.0) / 6.0; </p> </blockquote> <blockquote> <p> double sinc2 = 1.0 - x2 /6.0 + x2*x2 / 120.0; </p> </blockquote> <p> in some cases sinc1 provides better precision compared to sinc2 </p> <blockquote> <p> x generated with </p> </blockquote> <blockquote> <p> double x = sqrt(sqrt(std::numeric_limits&lt;double&gt;::epsilon())); for (int i = 0; x &gt; sqrt(std::numeric_limits&lt;double&gt;::epsilon()); i++) { </p> <blockquote> <p> x *= 0.99876765378657564; </p> </blockquote> <p> } </p> </blockquote> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/13603 Trac 1.4.3 John Maddock Sun, 17 Jun 2018 18:20:16 GMT https://svn.boost.org/trac10/ticket/13603#comment:1 https://svn.boost.org/trac10/ticket/13603#comment:1 <ul> <li><strong>status</strong> <span class="trac-field-old">new</span> → <span class="trac-field-new">closed</span> </li> <li><strong>resolution</strong> → <span class="trac-field-new">fixed</span> </li> </ul> <p> Thanks, applied in <a class="ext-link" href="https://github.com/boostorg/math/commit/658945d50822adae83d77083a559e785ce18609c"><span class="icon">​</span>https://github.com/boostorg/math/commit/658945d50822adae83d77083a559e785ce18609c</a> along with better tests. </p> Ticket