Chapter 5: Problem 1
Use the recursion formulas to calculate (a) \(T_{4}, T_{5}\) and (b) \(H_{4}, H_{5}\)
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Chapter 5: Problem 1
Use the recursion formulas to calculate (a) \(T_{4}, T_{5}\) and (b) \(H_{4}, H_{5}\)
These are the key concepts you need to understand to accurately answer the question.
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Prove that the transpose of an orthogonal matrix is an orthogonal matrix.
For each of the following systems \(A \mathbf{x}=\mathbf{b},\) find all least squares solutions: (a) \(A=\left(\begin{array}{rr}1 & 2 \\ 2 & 4 \\ -1 & -2\end{array}\right), \quad \mathbf{b}=\left(\begin{array}{l}3 \\ 2 \\ 1\end{array}\right)\) (b) \(A=\left(\begin{array}{rrr}1 & 1 & 3 \\ -1 & 3 & 1 \\ 1 & 2 & 4\end{array}\right), \quad \mathbf{b}=\left(\begin{array}{r}-2 \\ 0 \\\ 8\end{array}\right)\)
Let \(S\) be a subspace of an inner product space \(V\) Let \(\left\\{\mathbf{x}_{1}, \ldots, \mathbf{x}_{n}\right\\}\) be an orthogonal basis for \(S\) and let \(\mathbf{x} \in V .\) Show that the best least squares approximation to \(\mathbf{x}\) by elements of \(S\) is given by $$\mathbf{p}=\sum_{i=1}^{n} \frac{\left\langle\mathbf{x}, \mathbf{x}_{i}\right\rangle}{\left\langle\mathbf{x}_{i}, \mathbf{x}_{i}\right\rangle} \mathbf{x}_{i}$$
Verify that the Legendre polynomial \(P_{n}(x)\) satisfies the second-order equation $$\left(1-x^{2}\right) y^{\prime \prime}-2 x y^{\prime}+n(n+1) y=0$$ for \(n=0,1,2\)
A (real or complex) scalar \(u\) is said to be an \(n\) th root of unity if \(u^{n}=1\) (a) Show that if \(u\) is an \(n\) th root of unity and \(u \neq 1\) then $$1+u++u^{2}+\cdots+u^{n-1}=0$$ \\[ \left[\text {Hint}: 1-u^{n}=(1-u)\left(1+u+u^{2}+\cdots+u^{n-1}\right)\right] \\] (b) Let \(\omega_{n}=e^{\frac{2 \pi i}{n}} .\) Use Euler's formula \(\left(e^{i \theta}=\right.\) \(\cos \theta+i \sin \theta)\) to show that \(\omega_{n}\) is an \(n\) th root of unity. (c) Show that if \(j\) and \(k\) are positive integers and if \(u_{j}=\omega_{n}^{j-1}\) and \(z_{k}=\omega_{n}^{-(k-1)},\) then \(u_{j}, z_{k},\) and \(u_{j} z_{k}\) are all \(n\) th roots of unity
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