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    STUDIA MATHEMATICA - Issue no. 2 / 2012  
         
  Article:   SOME PROPERTIES ON GENERALIZED CLOSE-TO-STAR FUNCTIONS.

Authors:  .
 
       
         
  Abstract:  

Let f(z) = a1z+a1z2 +... , a1 0, be regular in |z| < 1 and have there no zeros except at the origin. Reade ([3]) and the Sakaguchi ([2]) showed that a necessary and sufficient condition for f(z) to be a member of the class C(k) is that f(z) has a representation of the form

f(z) = s(z)(p(z))k

where s(z) is a regular function starlike with respect to the origin for |z| < 1, k is a positive constant, and p(z) is a regular function with positive real part in |z| < 1. The class of close-to-star functions introduced by Reade ([4]) is equivalent to C(1). In this paper we define the class C(k, A,B) (−1 £ B < A £ 1, k is positive constant) which contains the functions of the form

f(z) = s(z)(p(z))k

where s(z) is a regular Janowski starlike function, and p(z) is a regular functionwith positive real part in |z| < 1. The aim of this paper is to give some propertiesand distortion theorems for this class.

Mathematics Subject Classification (2010): 30C45.

Keywords: Distortion theorem, radius of starlikeness.

 
         
     
         
         
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