MatN_Lab2_ex1.4

clear
close
clc

n=input('Hello, input number: ')
h=1/(n-1);
D=-30*eye(n)

for i=1:n-2
    D(i,i+1)=16;
    D(i,i+2)=-1;
end

D

for i=2:n
    D(i,i-1)=16;
    if i>=3
        D(i,i-2)=-1;
    end
end

D(n-1,n)=16


b=zeros(n,1);

hold on
for k=(1:n)
    b(k)=12*h^2*cos(2*pi*(k-1)/(n-1));
    x=D\b;
end

plot(1:n,x,'g*');

xlabel('k');
ylabel('x_k');
title('LES solution');