what is the difference between hold and plot of two curves in the same figure ?

 i want to plot cos(x) and sin(x) in the same figure, i have  two ways :
i can write for example :
X=0:pi,
Y=cos(X);
Z=sin(X);
Plot(X,Y,X,Z)
or the second way :
X=0:pi;
Y=cos(X);
Z=sin(Z);
Plot(X,Y)
Hold on
Plot(X,Z)
what is the difference between these two ways ?

Answer 1

[Honglei Chen]

If that's all you need, for the practical purpose, there isn't much difference. However, the internal settings in the two figures are different. For example, say you have another vector

W = cos(2*X);

and you want to plot it using

plot(X,W)

In the hold case, the new line will be added to the figure while in the other case, the axes will be cleared and the new plot contains only the new line.

HTH

[diadalina]

thank Mr.Honglei for your answer, I did not understand correctly, look to what i had written :

 figure(1) 
x = 0 :0.1 :2*pi;
   y1 = sin(x);
 y2 = cos(x);
W = cos(2*x);
plot(x,W)
 plot(x,y1,x,y2)
 figure(2)
  plot(x,y1)
 hold on
 plot(x,y2)
 plot(x,W)
i can't see the difference ?

[Honglei Chen]

Isn't one of them has 3 curves and the other only 2?

[diadalina]

no, they have 3 curves,i want to know the difference when i use plot and when i use hold on ?