INITIAL COEFFICIENT BOUNDS ON A SUBCLASS OF BOUNDED TURNING FUNCTIONS Rcos ASSOCIATED WITH COSINE FUNCTION
Tsukuba Journal of Mathematics, vol.49, no.2, pp.167-180, 2025 (ESCI, Scopus)
- Publication Type: Article / Article
- Volume: 49 Issue: 2
- Publication Date: 2025
- Doi Number: 10.21099/tkbjm/20254902167
- Journal Name: Tsukuba Journal of Mathematics
- Journal Indexes: Emerging Sources Citation Index (ESCI), Scopus
- Page Numbers: pp.167-180
- Keywords: Analytic functions, coe‰cient bounds, cosine function, Hankel determinant, subordination, successive coe‰cients di¤erence, Zalcman functional
- Bursa Uludag University Affiliated: Yes
Abstract
In the present paper, we investigate some initial coe‰cient bounds on a subclass of bounded turning functions Rcos associated with cosine functions. Also, we obtain the initial coe‰cient bounds for the first five coe‰cients of the functions that belong to these subclass Rcos. Further, initial consecutive coe‰cients module di¤erence estimates for the subclass Rcos is studied. Moreover, we determine the upper bound of Zalcman functional for the subclass Rcos for the case n = 3, showing that the Zalcman conjecture holds for these values.