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Zbl 0717.26014
Sándor, J.
On the identric and logarithmic means.
(English)
[J] Aequationes Math. 40, No.2-3, 261-270 (1990). ISSN 0001-9054; ISSN 1420-8903/e

After a survey of existing results, several new ones are offered for the identric mean $I(a,b)=e\sp{-1}(a\sp{-a}b\sp b)\sp{1/(b-a)}\quad (a\ne b),\quad I(a,a)=a,$ the logarithmic mean $L(a,b)=(b-a)\ln\sp{- 1}(b/a)\quad (a\ne b),\quad L(a,a)=a\quad (a>0,\quad b>0)$ and the arithmetic and geometric mean; for instance $$L(a,b)I(a,b)\sp{t- 1}<L(a,b)(b\sp t-a\sp t)/(t(b-a))<(a\sp t+b\sp t)/2\quad (a\ne b,\quad t\ne 0).$$ Logarithmic convexity and integral representations of the above means are used. \par The definition of a new mean'' is unfortunately misprinted: it should be $$J(a,b):=1/I(1/a,1/b)\quad (=\quad e(b\sp aa\sp{-b})\sp{1/(a- b)}\text{ for } b\ne a,\quad J(a,a)=a).$$
[J.Aczél]
MSC 2000:
*26D15 Inequalities for sums, series and integrals of real functions
26A51 Convexity, generalizations (one real variable)
26A48 Monotonic functions, generalizations (one real variable)

Keywords: arithmetic mean; integral mean; monotonic functions; inequalities; identric mean; logarithmic mean; geometric mean; Logarithmic convexity

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