(a) (7%) Compute the quantity A given below where the Fourier transform of f1(t) is given in the following figure (a).

接下來前段是背景知識介紹,之後才是提問)In solving the linear equation Ax=b for a igiven , instead of using the elemnentary row operations (i.e. the Gauss eliminations) to manipulate the equation, we may also apply the QR factorization to the equation to get QRx = b, which implies further QTQRx = QTb. Since QTQ = In, it gives Rx = QTb. Thus, according to the result of(a), when all columns of A are linearly independent, the square matrix R is nonsingular and so the solution x =b is obtained. It seems that we may summarize the above argument as the following statement:Given , where all columns of A are assumed linearly independent, then solution to the equation Ax = o can always be computed from x = , where Q and R are matrices obtained from the @R factorization of A. However, the simple example shows that the summary is incorrect because, according to the summary, the solution is x= and obviously it does not satisfy the original equation. (b) (5%) What is the error (or are the errors) in the argument right before the summary to make it incorrect?

題組內容

(a) (7%) Compute the quantity A given below where the Fourier transform of f₁(t) is given in the following figure (a).

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