%plot 6
t=0:0.01:20;
x=t.^2.*exp(-t).*sin(10*t);
subplot(2,2,1);
plot(t,x,'k');
xlim([0 10]);ylim([-0.6 0.6]);
grid on;
x=t.^4.*exp(-2*t).*sin(5*t);
subplot(2,2,2)
plot(t,x,'k');xlim([0 6]);ylim([-0.6 0.6]);
grid on;
x=t.*exp(-t).*sin(4*t);
subplot(2,2,3)
plot(t,x,'k');xlim([0 6]);ylim([-0.6 0.6]);
grid on
grid on;x=exp(-t).*sin(10*t);
subplot(2,2,4)
plot(t,x,'k');xlim([0 6]);ylim([-1 1]);
grid on;