New Refinements of Cusa-Huygens inequality

Christophe Chesneau, Marko Kostic, Branko Malesevic +2

In the paper, we refine and extend Cusa-Huygens inequality by simple functions. In particular, we determine sharp bounds for $\sin (x)/x$ of the form $(2+\cos (x))/3-(2/3-2/\pi ){\rm Y}(x)$…