A Double Inequality for the Trigamma Function and Its Applications

作者:Yang, Zhen Hang; Chu, Yu Ming*; Tao, Xiao Jing
来源:Abstract and Applied Analysis, 2014, 2014: 702718.
DOI:10.1155/2014/702718

摘要

We prove that p = 1 and q = 2 are the best possible parameters in the interval (0, infinity) such that the double inequality (e(p/(x+1)) - e(-p/x))/2p < psi'(x + 1) < (e(q/(x+1)) - e(-q/x))/2q holds for x > 0. As applications, some new approximation algorithms for the circumference ratio pi and Catalan constant G = Sigma(infinity)(n=0) ((-1)(n)/(2n + 1)(2)) are given. Here, psi' is the trigamma function.