International Journal of Mathematics and Mathematical Sciences 
Volume 28 (2001), Issue 9, Pages 557-560
doi:10.1155/S0161171201011656

A sufficient condition for starlikeness of order α

Petru T. Mocanu1 and Gh. Oros2

 1Department of Mathematics, Babes-Bolyai University, Cluj-Napoca 3400, Romania
2Department of Mathematics, University of Oradea, Oradea 3700, Romania
Received 28 January 2001; Revised 12 June 2001

Abstract

We obtain a sufficient condition for starlikeness of order α, |f′(z)−λ(f(z)/z)+λ−1|<M=Mn(λ,α), where λ∈[0,1], α∈[0,1] and the function f(z)=z+an+1zn+1+⋯ is analytic in the unit disc U.