a) LPF is a rect function in the frequency domain and sinc function in the time domain.

b) Here is the code I used

%E416_p223%rjb %8/20/2014%HW problem 2.235 CS Haykin clearBT =100; % 5,T=1;B=BT/T;delta_t = T/200 %T/100, T/150,T/200, T/1000t = [-6*T:delta_t:6*T];%pulse of unit amplitudex = zeros(size(t));index = find(abs(t)