  Chen and Cheung [C.-P. Chen, W.-S. Cheung, Sharpness of Wilker and Huygens
type inequalities, J. Inequal. Appl. 2012 (2012) 72,
\url{http://dx.doi.org/10.1186/1029-242X-2012-72}] established sharp Wilker and
Huygens-type inequalities. These authors also proposed three conjectures on
Wilker and Huygens-type inequalities. In this paper, we consider these
conjectures. We also present sharp Wilker and Huygens-type inequalities.

Classical Analysis and ODEs