function root=GoldenF(f,a,b,eps)
% 黃金分割法求函數(shù)f在[a,b]上的一個零點
% 函數(shù)名：f
% 區(qū)間左端點a
% 區(qū)間右端點b
% 根的精度:eps
% 求出的函數(shù)零點：root
if(nargin==3)
    eps=1.0e-4;
end

f1=subs(sym(f),findsym(sym(f)),a);
f2=subs(sym(f),findsym(sym(f)),b);
if(f1==0)
    root=a;
end
if(f2==0)
    root=b;
end

if(f1*f2>0)
    disp('兩端點函數(shù)值乘積大于0!');
    return;
else   
    t1=a+(b-a)*0.382;t2=a+(b-a)*0.618;
    f_1=subs(sym(f),findsym(sym(f)),t1);
    f_2=subs(sym(f),findsym(sym(f)),t2); 
    tol=abs(t1-t2);
    while(tol>eps)                           %精度控制
     if(f_1*f_2<0),a=t1;b=t2;
     else fa=subs(sym(f),findsym(sym(f)),a);         
      if(f_1*fa>0),a=t2;else b=t1;end,end
        t1=a+(b-a)*0.382;t2=a+(b-a)*0.618;
        f_1=subs(sym(f),findsym(sym(f)),t1);
        f_2=subs(sym(f),findsym(sym(f)),t2); 
        tol=abs(t2-t1);
    end
  root=(t1+t2)/2;                             %輸出根
end