Janteng, Aini; Halim, Suzeini Abdul; Darus, Maslina Coefficient inequality for a function whose derivative has a positive real part. (English) Zbl 1134.30310 JIPAM, J. Inequal. Pure Appl. Math. 7, No. 2, Paper No. 50, 5 p. (2006). Summary: Let \(\mathcal R\) denote the subclass of normalised analytic univalent functions \(f\) defined by \(f(z)=z+\sum^\infty_{n=2}a_nz^n\) which satisfy \[ \mathrm{Re}\{f'(z)\}>0 \] where \(z\in{\mathcal D}=\{z: |z|<1\}\). The object of the present paper is to introduce the functional \(|a_2a_4-a^2_3|\). For \(f\in\mathcal R\), we give sharp upper bound on \(|a_2a_4-a^2_3|\). Cited in 92 Documents MSC: 30C45 Special classes of univalent and multivalent functions of one complex variable (starlike, convex, bounded rotation, etc.) 30C50 Coefficient problems for univalent and multivalent functions of one complex variable Keywords:Fekete-Szegö functional; Hankel determinant; convex and starlike functions; positive real functions PDFBibTeX XMLCite \textit{A. Janteng} et al., JIPAM, J. Inequal. Pure Appl. Math. 7, No. 2, Paper No. 50, 5 p. (2006; Zbl 1134.30310) Full Text: EuDML EMIS