a = 2.01;
x = 0:.1:200;
y = (1/(4*pi^2*(4-a^2)))*cos(2*pi*a*x) + (1/(4*pi^2*(a^2-4)))*cos(4*pi*x);
plot(x,y)
xlabel('t')
ylabel('x(t)')
title('Plot of x(t) = 1/(4 * pi^2 (4 - 2.01^2) * cos(2 * pi * 2.01 * t) + 1/(4 * pi^2 (2.01^2 - 4) * cos(4 * pi * t)')