QCD CORRECTIONS FROM THE TOP-QUARK TO RELATIONS BETWEEN ELECTROWEAK PARAMETERS UP TO ORDER ALPHA(2)(S)

The vacuum polarization functions Pi(q(2)) of charged and neutral gaug e bosons that arise from top and bottom quark loops lead to important shifts in relations between electroweak parameters that can be measure d with ever-increasing precision. The large mass of the top quark allo ws approximation of these functions through the first two terms of an expansion in M(Z)(2)/M(t)(2). The first three terms of the Taylor seri es of Pi(q(2)), evaluated analytically up to order alpha(s)(2). Result s for the subleading contributions to hr and the effective mixing angl e sin(2)<(Theta)over bar> are presented.