A REFINEMENT OF SCHWARZ'S LEMMA AT THE BOUNDARY

Abstract

We study a boundary version of the Schwarz lemma for analytic functions. In addition, an analytic function satisfying the equality case is found by deducing inequalities connected with the modulus of the derivative of analytic functions at a boundary point of the unit disk. In these inequalities, we consider some coefficients used in the Taylor expansion of the function. In the last theorem, by analyzing the Taylor expansion about two points, we obtain the modulus of the derivative of the function at point 1.