Radius of Starlikeness for Classes of Analytic Functions

We consider normalized analytic function f on the open unit disk for which either R e f ( z ) / g ( z ) > 0 , | f ( z ) / g ( z ) - 1 | < 1 or R e ( 1 - z 2 ) f ( z ) / z > 0 for some analytic function g with R e ( 1 - z 2 ) g ( z ) / z > 0 . We have obtained the radii for these functions to belong to various subclasses of starlike functions. The subclasses considered include the classes of starlike functions of order α , lemniscate starlike functions and parabolic starlike functions.