// Polynome de Lagrange Q_2 et ses derivees
function [FP,DxFP,DyFP] = Q2(x,y)


  FP = zeros(9,1); DxFP = zeros(9,1); DyFP = zeros(9,1);

  FP(1,1) =  (1-x)*x*(1-y)*y/4;
  FP(2,1) = -(1+x)*x*(1-y)*y/4;
  FP(3,1) =  (1+x)*x*(1+y)*y/4;
  FP(4,1) = -(1-x)*x*(1+y)*y/4;
  FP(5,1) = -(1-x^2)*(1-y)*y/2;
  FP(6,1) =  (1+x)*x*(1-y^2)/2;
  FP(7,1) =  (1-x^2)*(1+y)*y/2;
  FP(8,1) = -(1-x)*x*(1-y^2)/2;
  FP(9,1) =  (1-x^2)*(1-y^2);

  DxFP(1,1) =  (1-2*x)*(1-y)*y/4;
  DxFP(2,1) = -(1+2*x)*(1-y)*y/4;
  DxFP(3,1) =  (1+2*x)*(1+y)*y/4;
  DxFP(4,1) = -(1-2*x)*(1+y)*y/4;
  DxFP(5,1) =   x*(1-y)*y;
  DxFP(6,1) =  (1+2*x)*(1-y^2)/2;
  DxFP(7,1) =  -x*(1+y)*y;
  DxFP(8,1) = -(1-2*x)*(1-y^2)/2;
  DxFP(9,1) = -2*x*(1-y^2);

  DyFP(1,1) =  (1-x)*x*(1-2*y)/4;
  DyFP(2,1) = -(1+x)*x*(1-2*y)/4;
  DyFP(3,1) =  (1+x)*x*(1+2*y)/4;
  DyFP(4,1) = -(1-x)*x*(1+2*y)/4;
  DyFP(5,1) = -(1-x^2)*(1-2*y)/2;
  DyFP(6,1) = -(1+x)*x*y;
  DyFP(7,1) =  (1-x^2)*(1+2*y)/2;
  DyFP(8,1) =  x*(1-x)*y;
  DyFP(9,1) = -2*(1-x^2)*y;

endfunction


