Whats the purpose of cos function?

Question

Pooja 2013-6-26

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/80327-whats-the-purpose-of-cos-function

%build the matrix
n = 0:N-1;
for k = 0:N-1
     if (k>0)
        C(k+1,n+1) = cos(pi*(2*n+1)*k/2/N)/sqrt(N)*sqrt(2);
     else
        C(k+1,n+1) = cos(pi*(2*n+1)*k/2/N)/sqrt(N);
     end   
  end

Is that because of using dct ?or cos function have any other functions ?

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Answer 1

Walter Roberson 2013-6-26

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https://ww2.mathworks.cn/matlabcentral/answers/80327-whats-the-purpose-of-cos-function#answer_90070

The cosine function was originally created as a "make work" project for medieval tutors, to convince patrons that the tutors knew something exotic that was worth paying for; in this, the trig functions replaced the earlier Latin Squares Mysteries Strategic Work Initiative.

Later, cosine functions were found to have some useful mathematical properties.