plot differential equation (ODE)

please help me to plot this equation y=5*cos(sqrt(2)*x)

This is my plotting but it is not correct

x=0:1:20;

y=zeros(length(x));

for i=1:length(x)

    y(i)=5*cos(sqrt(2)*x(i));
end

figure,

plot(y(1:20));

[Azzi Abdelmalek]

Your title don't correspond to your question

[Mukhtar Hussain]

Try this if it works

x=0:0.01:20;

y=zeros(length(x));

for i=1:length(x)

    y(i)=5*cos(sqrt(2)*x(i));

end

figure;

plot(x,y);

Answer 1

[Azzi Abdelmalek]

It's not y=zeros(length(x)) but y=zeros(1,length(x));and dont use i ( reserved to complex numbers)

 x=0:1:20;
 y=zeros(1,length(x));
 for ii=1:length(x)
   y(ii)=5*cos(sqrt(2)*x(ii));
 end
 figure,
 plot(y);