Some results for a certain class of holomorphic functions at the boundary of the unit disc

We consider a version of the boundary Schwarz Lemma on a certain class which is denoted by K(?). For the function f(z) = z + c2z2 + c3z3 + ... defined in the unit disc E such that the function f(z) belongs to the class K(?), we estimate from below the modulus of the angular derivative of the function z f (z) f(z) at the boundary point b with b f (b) f(b) = 1 1+? . Moreover, we get Schwarz Lemma for the class K(?). We also investigate some inequalities obtained in terms of sharpness.