Editing Digamma function (section)

==Gauss's digamma theorem==
For positive integers {{mvar|r}} and {{mvar|m}} ({{math|''r'' < ''m''}}), the digamma function may be expressed in terms of [[Euler's constant]] and a finite number of [[elementary function]]s<ref>{{cite journal|first1=Junesang|last1=Choi|first2=Djurdje|last2=Cvijovic|title=Values of the polygamma functions at rational arguments|journal=Journal of Physics A|year=2007|volume=40|pages=15019|doi=10.1088/1751-8113/40/50/007|number=50|bibcode=2007JPhA...4015019C |s2cid=118527596 }}</ref>

:<math>\psi\left(\frac{r}{m}\right) = -\gamma -\ln(2m) -\frac{\pi}{2}\cot\left(\frac{r\pi}{m}\right) +2\sum_{n=1}^{\left\lfloor \frac{m-1}{2} \right\rfloor} \cos\left(\frac{2\pi nr}{m} \right) \ln\sin\left(\frac{\pi n}{m}\right) </math>

which holds, because of its recurrence equation, for all rational arguments.