% solucion de la ecuacion de ondas unidimensional
% la cuerda vibrante
%clear all


if (ej==1)
  N = 1;
  a = [1];
  b = [0];
elseif (ej == 2)
  N = 1;
  a = [0];
  b = [1];
elseif (ej == 3)
  N = 2;
  a = [1 0.2];
  b = [0 0];
else
  N = 5;
  a = [1 0.2 0 0 0.1];
  b = [0 0   0 0 0];
end

n = [1:N];
x = [0:.01:1];

npix = pi*n' * x;

senox = sin(npix);

for t=0:.02:4
  u = (a.*cos(n*pi*t) + b.*sin(n*pi*t)) * senox;
  plot(x,u);
  axis([0 1 -2 2])
  if (t==0)
    pause
  else
    pause(0.05)
  end
end

pause
if (ej < 3)
  return
end

for t=0:.02:4
  u1 = (a(1).*cos(1*pi*t)) * senox(1,:);
  if (ej==3)
    u2 = (a(2).*cos(2*pi*t)) * senox(2,:);
  else
    u2 = (a(5).*cos(5*pi*t)) * senox(5,:);
  end

  u  = u1 + u2;
  plot(x,u,x,u1,x,u2);
  axis([0 1 -2 2])
  if (t==0)
    pause
  else
    pause(0.1)
  end
end