please how to write this in matlab?

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Abdelrazzak rifai 2018-4-16

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评论： Abdelrazzak rifai 2018-4-16

fourier function

define a sum of cosine waves f=8 HZ
build it's plot in time domain
build the plot of it's magnitude spectrumi don't understand how to use the arry in matlab :( :(

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Answer 1

Ngoc Thanh Hung Bui 2018-4-16

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I dont really understand the problem, better more specifically

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Answer 2

KALYAN ACHARJYA 2018-4-16

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编辑：KALYAN ACHARJYA 2018-4-16

在 MATLAB Online 中打开

 % Are you looking for this one 
t=0:1:115;
fs=500 % Assumed Sampling Frequency
f=8; % Given 8 Hz
cw=cos(2*pi*f/fs*t);
subplot(121);stem(cw,'r'); title('Time Domain');
%Read in Signal Processing Book How to find Magnitute Response
fftLength=512;
sigLength=length(cw);
win=rectwin(sigLength)'; % Window Selection 'Ractangular'
y=fft(cw.*win,fftLength);
length=fftLength/2+1;
% Magnitude Response 
subplot(122);plot([1:length]*fs/(2*length),abs(y(1:length)));
title('Magnitude Response');

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Abdelrazzak rifai 2018-4-16

在 MATLAB Online 中打开

the professor gave us :

 #s=fft(U);
build plot of complex spectrum

1:M=√a^2+b^2

2:MS=abs(S)

3: plot(ms)

4:he gave us:complex exponential and Fourier function and he told us using vector and bla bla bla..

Abdelrazzak rifai 2018-4-16

x(t)=A*cos(2*pi*frequency*time+pi/6)

pi/6=30 phase shift of the cosine in degree
A=1,frequency=8,phase=pi/6; or 30 degree,time=0:1:115;(but how can i understand these step?please..so how can i build the magnitude spectrum?i want to understand please..

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