Fourth Hankel determinant and logarithmic coefficients for starlike functions associated with the cosine function

• Date: 2026
• Main Authors: Ali, Rashid, Raza, Mohsan, Bulboacă, Teodor
• Format: Article
• Language: English
• Published: Institute of Mathematics, NAS of Ukraine 2026
• Online Access: https://umj.imath.kiev.ua/index.php/umj/article/view/9403
• Journal Title: Ukrains’kyi Matematychnyi Zhurnal

UDC 517.53, 517.54 Let $\mathcal{\mathcal{S}}_{\cos}^{\ast}$ be a class of normalized analytic functions $f$ in an open unit disk $\mathbb{D}$ satisfying the subordination $\dfrac{zf^{\prime}(z)}{f(z)}\prec\cos z.$ The aim of the present article is to find upper bounds for the module of some coeffic...