function [x,ile]=bissect(fun, a,b,epsilon)
f=fcnchk(fun);
i=0;
while 1
    i=i+1;
    p=(a+b)/2;
    if f(a)*f(p)<0
        b=p;
    else
        a=p;
    end
    if abs(f(p))<epsilon
        x=p;
        ile=i;
        break
    end
end