my plot is not sinusoidal wave

hello can you please help me?? when i type this code i only get an horizontal line

i don`t know where is my mistake

the code

clc
sigma0=0;
sigma1=100;
sigma2=500;
el=0.5*0.0001;
L=1*0.0001 ;
h=0.5*0.0001;
a=1;
rho=1000;
g=10;
t=300;
m=4;
n=4;
x=0:100:5000;
A=(pi*((m/el)^(2)+(n/L)^(2))^(0.5));
B0=(g*A+(sigma0/rho).*A^3).*atan(A*h);
C0=B0^(0.5); 
Z0=a*cos(C0.*t).*cos((m*pi.*x)/el);
B1=(g*A+(sigma1/rho)*A^3)*atan(A*h*1/180);
C1=B1^(0.5); 
Z1=a*cos(C1.*t).*cos((m*pi.*x)/el);
B2=(g*A+(sigma2/rho)*A^3)*atan(A*h);
C2=B2^(0.5); 
Z2=(a*cos(C2.*t).*cos((m*pi.*x)/el));
subplot(2,2,1)
plot(x,Z0,'r',x,Z1,'g',x,Z2,'b');
xlabel(' paroi x');
ylabel(' elevation z');
legend('sigma=0',' sigma=100',' sigma=500')

Answer 1

[darova]

Your argument for cos is too big

Try

x = linspace(0,5e-5,50);

The result

[MOUNIBA REDAH]

Ok thank you for your help

I will try it

Answer 2

[Giuseppe Inghilterra]

Hi,

the argument of cosine "(m*pi.*x)/el" returns you always one.

This happens because your cosine argument is expressed in the form 'k*pi' with k = even integer number. In this case cos(k*pi) (with k = even integer number) returns you always one.

If you try to change parameter m or el or step of x such that m*x/el is not an even interger number you obtain a wave plot.

For example with: x = 0:pi:5000, you obtain the following result:

[MOUNIBA REDAH]

Ok thank you for your help

I see now where is my mistake