clear;
clc;

N=100;
x=linspace(-pi,pi,N);

y=cos(x);

figure(1);
plot(x,y)
xlabel('x')
ylabel('y')
hold on

% Def 2 points
x1=1;
x2=1.1;
y1=cos(x1);
y2=cos(x2);
plot(x1,y1,'ro');
plot(x2,y2,'ro');

%Differentiate
deltaY=y2-y1;
deltaX=x2-x1;
dydx=deltaY/deltaX;
plot(1,dydx,'ro');

%Compare
answer=-sin(x1);
trueDiff=sin(x1);
error=abs(answer-trueDiff);
plot(x,-sin(x));
hold off