function [x,xv,k]=secanti(fun,x0,x1)
fx0=fun(x0);
fx1=fun(x1);
xv=[x0,x1];
for k=1:1000
    x=x1-(x1-x0)/(fx1-fx0)*fx1;
    xv=[xv x];
    inc=abs(x-x1);
    if inc < 1.e-10, return, end
    x0=x1; fx0=fx1;
    x1=x; fx1=fun(x);
end
