Published in:
Open Access
01-12-2016 | Research
Optimal bounds for two Sándor-type means in terms of power means
Authors:
Tie-Hong Zhao, Wei-Mao Qian, Ying-Qing Song
Published in:
Journal of Inequalities and Applications
|
Issue 1/2016
Abstract
In the article, we prove that the double inequalities \(M_{\alpha }(a,b)< S_{QA}(a,b)< M_{\beta}(a,b)\) and \(M_{\lambda }(a,b)< S_{AQ}(a,b)< M_{\mu}(a,b)\) hold for all \(a, b>0\) with \(a\neq b\) if and only if \(\alpha\leq\log 2/[1+\log2-\sqrt{2}\log(1+\sqrt{2})]=1.5517\ldots\) , \(\beta\geq5/3\), \(\lambda\leq4\log2/[4+2\log2-\pi]=1.2351\ldots\) and \(\mu\geq4/3\), where \(S_{QA}(a,b)=A(a,b)e^{Q(a,b)/M(a,b)-1}\) and \(S_{AQ}(a,b)=Q(a,b)e^{A(a,b)/T(a,b)-1}\) are the Sándor-type means, \(A(a,b)=(a+b)/2\), \(Q(a,b)=\sqrt{(a^{2}+b^{2})/2}\), \(T(a,b)=(a-b)/[2\arctan((a-b)/(a+b))]\), and \(M(a,b)=(a-b)/[2\sinh ^{-1}((a-b)/(a+b))]\) are, respectively, the arithmetic, quadratic, second Seiffert, and Neuman-Sándor means.