I stumbled upon this using Sage, but developers there have traced it to a problem in GiNaC by running the following in ginsh:<div><br></div><div>&gt; atan2(-Pi,0);</div><div><br></div><div>The response is:</div><div><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 12px; ">power::eval(): division by zero </span></div>
<div><font class="Apple-style-span" face="arial, sans-serif" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><font class="Apple-style-span" face="arial, sans-serif" size="3"><span class="Apple-style-span" style="font-size: 12px;">atan2 appears to work for other values, including (positive) (Pi,0), but (-Pi,0) fails.</span></font></div>
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