%filename:c2_1_1.m
h=0.1*pi;
x=0:h:2*pi;
y=sin(x);
dy1=diff(y)/h;
dy2=diff3p(y,h);
dy0=cos(x);
error1=norm(dy1-dy0(1:20));
error2=norm(dy2-dy0);

dyo2=diff3p(y,h,2);%dy3=ppval(fnder(spline(x,y),x);
erroro2=norm(dyo2+y);
plot(x,-y,'r-',x,dyo2,'o')
%error3=norm(dy3-dy0);