SUBKELAS FUNGSI CEMBUNG DAN FUNGSI BAK-BINTANG

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Date
1993-09
Authors
RAJA MAAMOR SHAH, RAJA LAILATUL ZURAIDA
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Abstract
Denote by S the class of functions f analytic and univalent in the open unit disk U = { z : lzl < 1 } and normalised such that f(O) = 0 = f' (0) - 1. For k in [0, 1], let B(k) denote the class of functions f in S which satisfy I A2 (~) - A (~) I ~ k under Marty transformations 2 3 F(z) = [ f((z+~)/(1+~z)) - f(~) ] / (1-l~l 2 )f' (~) , 1~1 < 1. Fork= 0, we find the general form and sharp coefficient estimates for functions in the class B(O). We determine that B(O) consists of convex functions. We also consider the class R(a) consisting of analytic and normalised functions f in U which satisfy the condition Re { f' (z) + azf"(z) } > 0, z e U and a ~ 0. We find the value of a such that R(a) is a subclass of starlike functions in U. Further,.- we generalize the condition of R(a). Denote by R(a,/3) the subclass of analytic and normalised functions F in U which satisfy Re { F' (z) + azF"(z) } > /3, z e U, f3 < 1 and a = - 1 - 1+-c > 0. We obtain the values of f3 and c so that R(a) consists of starlike functions in U. For this class, we obtain sharp coefficient estimates and the lower and upper bounds of IF(z) 1. X --------- --------------- LaStly, let T l 1 ~c , f3 J be the class of analytic and normalised functions F in U which satisfy Re { ei0 ( F' (z) + azF" (z) - {3 ) } > 0, for some real number 0 , z e U and f3 < 1. We obtain sharp coefficient estimates for functions in .
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SUBKELAS FUNGSI CEMBUNG DAN FUNGSI BAK-BINTANG
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