Chi
From specialfunctionswiki
The hyperbolic cosine integral $\mathrm{Chi} \colon (0,\infty) \rightarrow \mathbb{R}$ is defined by the formula $$\mathrm{Chi}(z)=-\displaystyle\int_z^{\infty} \dfrac{\mathrm{cosh}(t)}{t} \mathrm{d}t=\gamma + \log(z) + \displaystyle\int_0^z \dfrac{\mathrm{cosh}(t)-1}{t} \mathrm{d}t,$$ where $\gamma$ denotes the Euler-Mascheroni constant, $\log$ denotes the logarithm, and $\mathrm{cosh}$ denotes the hyperbolic cosine function.
Graph of $\mathrm{chi}$ on $(0,5]$.
Domain coloring of analytic continuation of $\mathrm{chi}$.
