The adjacent sides of hyperbolic Lambert quadrilaterals
A Lambert quadrilateral $OABC$ in the real hyperbolic plane is a quadrilateral for which the angles $\widehat{AOB}$, $\widehat{OAC}$, and $\widehat{OBC}$ are all right. The author provides a sharp upper bound (in terms of $\mathrm{th}(OC)$) for $AC\cdot BC$, and both sharp lower and upper bounds in terms (in terms of $\mathrm{th}(OC)$) for $AC + BC$. He also proves some results regarding the Hölder convexity of the inverse hyperbolic sine function.
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