w=0:0.01:4*pi;
wp=6;
wn=1;N=4;ebi=0.5;
if abs(w)<=1
    CN=cos(N*acos(w/wp));
else
    CN=cosh(N*acosh(w/wp));
end
f=sqrt(1+(ebi*CN).^2);
H=1./f;hold on
%subplot(222)
plot(w/pi,H,'k'),axis([0,4,0,1.2])
title('The frequency response of The Chebyshev filter')
xlabel('w')
hold on