From a journalistic standpoint, including the formula would require a longer digression into contour integrals than the one clause the article currently contains.
It’s also not clear what license that image is available under.
> It’s also not clear what license that image is available under.
A plain image of mathematical equation is not copyrightable, it's literally the MathJax output of a LaTeX equation ({\displaystyle r=2\cos \left({\frac {1}{2}}{\frac {\oint _{|z-3\pi /8|=\pi /4}z/(\sin z-z\cos z-\pi /2)\,dz}{\oint _{|z-3\pi /8|=\pi /4}1/(\sin z-z\cos z-\pi /2)\,dz}}\right)}). It does not have any copyrightable artistic design. And to the nitpickers - the pixmap output of a font is also not copyrightable under U.S. copyright laws. Even if it is, Computer Modern is available under a free license. And even if it's not, pure facts - such as math formulas - are not copyrightable, it would be trivial to write down the identical equation using another program and font.
Copyright is not an inevitable, divine, or natural right, it is only an utilitarian tool adopted by the Constitution and lawmakers "to promote the Progress of Science and useful Arts." Thus, there always exist things that cannot be copyrighted. It's also why fair use of copyrighted works is conditionally allowed (not relevant to this case). The tendency of people to assume that every single piece of data is automatically controlled exclusively under copyright is frustrating.
It’s also not clear what license that image is available under.