xx=0:0.02:10;yy=xx;[x y]=meshgrid(xx,yy);
z=(x./(x+y) +1.96*1.96./(2*(x+y))-1.96*((x./(x+y).*(1-x./(x+y))+1.96*1.96./(4*(x+y)))./(x+y)).^0.5)./(1+1.96*1.96./(x+y));
surf(x,y,z)
按上面语句试试