how can i vary the frequency of the signal

i want to have a signal with variable frequency but i don't know how to do that. the code is

A=240;

d=6;

C=55*pi;

x=[0:1/100:10];

s=x.^3;

a=-(s.*d);

c=x.*C;

b=cos(c);

t=b.*(x.*(A*exp(a))); %the signal

Answer 1

[hosein Javan]

A=240;
d=6;
x=0:1e-4:1;
s=x.^3;
a=-(s.*d);

minfreq = 10; % minimum frequency(Hz)
maxfreq = 200; % maximum frequency(Hz)
w = 2*pi*(linspace(minfreq,maxfreq,length(x))); % array of linear-spaced frequency data vs x
b=cos(w.*x);                
t=b.*(x.*(A*exp(a))); %the signal

plot(x,t)

Answer 2

[David Hill]

A=240;
d=6;
x=[0:1/100:10];
s=x.^3;
a=-(s.*d);           
t=@(f)cos(f*x).*(x.*(A*exp(a))); %the signal
plot(x,t(55*pi));