%newton raphson 
clear all
clc

x=linspace(-pi/2,pi/2);
f=@(x) tan(x);
df=@(x) 1./cos(x)^2;
Nmax=100;
tol=sqrt(eps);
fplot(f)

[c] = NRAPH(f,df,x,Nmax,tol)
xline(c)
function [x0] = NRAPH(f,df,x,Nmax,tol)
   a=x(1);
   b=x(end);

    x0=a - sign(f(a))*(b-a)/(sign(f(b))-sign(f(a))); 
    k=1;
    e(1)=abs(f(x0));

    while k<Nmax && e(k)>tol
        x0= x0 - f(x0)/df(x0);
        k=k+1;
        e(k)=abs(f(x0));
    end
end