Chi

The hyperbolic cosine integral $\mathrm{chi} \colon (0,\infty) \rightarrow \mathbb{R}$ is defined by the formula $$\mathrm{chi}(z)=\gamma + \log(z) + \displaystyle\int_0^z \dfrac{\mathrm{cosh}(t)-1}{t} dt,$$ where $\gamma$ denotes the Euler-Mascheroni constant, $\log$ denotes the logarithm, and $\mathrm{cosh}$ denotes the hyperbolic cosine function.

• Coshintegral.png

  Graph of $\mathrm{chi}$ on $(0,5]$.