Some inequalities for starlike functions |
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Authors: | St Ruscheweyh V Singh |
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Affiliation: | 1. Mathematisches Institut, Universit?t Würzburg, D-8700, Würzburg, Federal Republic of Germany 2. Department of Mathematics, Punjabi University, 147002, Patiala, India
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Abstract: | For normalized starlike univalent functions in the unit disc we derive upper and lower estimates for certain differential expressions ofn-th order (including |zf′(z)/f(z)| forn=1) in terms of |f(z)|. Our results generalize and/or improve earlier ones by Twomey and Singh. The operators and methods applied come from the theory of the Peschl-Bauer differential equation. |
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