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Certain refinements of Jordan-type inequalities

Dipika P. Wagh1, Yogesh J. Bagul2, Narendra Swami1
1Department of Mathematics, Shri Jagdishprasad Jhabarmal Tibrewala University, Jhunjhunu, Rajasthan – 333010, India
2Department of Mathematics, K. K. M. College, Manwath, Dist: Parbhani (M. S.) – 431505, India
Copyright © Dipika P. Wagh, Yogesh J. Bagul, Narendra Swami. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We present new sharp bounds for the function \((\sin x)/x, \) thus refining the well-known Jordan-type inequalities in the literature. A polynomial-trigonometric approach is used to establish the bounds. The main results are based on the series expansions, monotonicity rules, and the bounds of the ratio of even indexed Bernoulli numbers. We also generalize our main results using the concept of stratification.

Keywords: Jordan’s inequality, sinc function, monotonicity rules, series expansion