Hi !!! what is wrong in my code ??

give me code of s(t) = cos(2*Π*100*t) + cos(2*Π*200*t).

t = 0:.01:1 % independent (time) variable

A = 8; % amplitude

f_1 = 2; % create a 2 Hz sine wave lasting 1 sec

s_1 = A*sin(2*pi*f_1*t);

f_2 = 4; % create a 4 Hz sine wave lasting 1 sec

s_2 = A*sin(2*pi*f_2*t);

%plot the 2 Hz sine wave in the top panel

subplot(3,1,1) ,plot(t, s_1)

title('2 Hz sine wave')

ylabel('Amplitude')

%plot the 4 Hz sine wave in the middle panel

subplot(3,1,2) , plot(t, s_2)

title('4 Hz sine wave')

ylabel('Amplitude')

%plot the summed sine waves in the bottom panel

subplot(3,1,3) , plot(t, s_1+s_2)

title('Summed sine waves')

ylabel('Amplitude')

xlabel('Time (s)')

[Stephen23]

http://web.archive.org/web/20201213190708/https://www.mathworks.com/matlabcentral/answers/692680-hi-what-is-wrong-in-my-code

Answer 1

[Star Strider]

It appears to run without error and gives what I consider the appropriate result.

What problems are you having with it?

If you want to plot:

give me code of    s(t) = cos(2*Π*100*t) + cos(2*Π*200*t).  

instead, make the appropriate substitutions for ‘A’, ‘f_1’, and ‘f_2’ in the code you posted, and change the sin calls to cos calls.

[Titu talukder]

t = 0:.01:1 % independent (time) variable

A = 8; % amplitude

f_1 = 2; % create a 2 Hz sine wave lasting 1 sec

c_1 = f1*cos(2*pi*f_1*t);

f_2 = 4; % create a 4 Hz sine wave lasting 1 sec

c_2 = f2*cos(2*pi*f_2*t);

%plot the 2 Hz cos wave in the top panel

subplot(3,1,1) ,plot(t, c_1)

title('2 Hz cos wave')

ylabel('Amplitude')

%plot the 4 Hz cos wave in the middle panel

subplot(3,1,2) , plot(t, c_2)

title('4 Hz cos wave')

ylabel('Amplitude')

%plot the summed sine waves in the bottom panel

subplot(3,1,3) , plot(t, c_1+c_2)

title('Summed cos waves')

ylabel('Amplitude')

xlabel('Time (s)')

error 1 : Undefined function or variable 'x'.

Error in Untitled6 (line 8)

plot(t,x);

error2: Undefined function or variable 'f1'.

Error in control1lab (line 4)

s_1 = f1*cos(2*pi*f_1*t);

[Star Strider]

Note that ‘A’ is the amplitude and ‘f_1’ and ‘f_2’ are the frequencies.

Look at ‘c_1’ and ‘c_2’ and make the appropriate substitutions, using the information in ‘s(t)’.

[Titu talukder]

if you dont mind , can you write the whole code here ? plz

[Star Strider]

Since this appears to be homework, the policy on MATLAB Answers is not to provide working code for homework problems.

The code you were given is in the context of:

Amplitude * cos(2*pi*Frequency*t)

for each term.

I will let you take it from there.

[Titu talukder]

you can send me in an email , plz

[e-mail]

[Star Strider]

I have given you all the help I can possibly give without writing the code for you.

Please re-read what I wrote and experiment using the hints I have provided.

[Star Strider]

That code ↓ should do what you want. It really was not that difficult!

Answer 2

[Titu talukder]

t = 0:.01:1;

A = 1;

fm1 = 100;

s1 = A*cos(2*pi*fm1*t);

fm2 = 200;

s2 = A*cos(2*pi*fm2*t);

subplot(3,1,1) ,plot(t, s1);

title('cos(2*pi*100*t)');

ylabel('Amplitude');

subplot(3,1,2) , plot(t, s2);

title('cos(2*pi*200*t)');

ylabel('Amplitude');

subplot(3,1,3);

plot(t, s1+s2);

title('S(t)');

ylabel('Amplitude');

xlabel('Time (s)');