Chapter 11: Problem 29
Let \(W\) be the subspace of \(\mathbf{R}^{3}\) spanned by (1,1,0) and \((0,1,1) .\) Find a basis of the annihilator of \(W\).
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Chapter 11: Problem 29
Let \(W\) be the subspace of \(\mathbf{R}^{3}\) spanned by (1,1,0) and \((0,1,1) .\) Find a basis of the annihilator of \(W\).
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Show that if \(\phi \in V^{*}\) annihilates a subset \(S\) of \(V\), then \(\phi\) annihilates the linear span \(L(S)\) of \(S\). Hence, \(S^{0}=[\operatorname{span}(S)]^{0}\).
Let \(V\) be the vector space of polynomials of degree \(\leq 2\). Let \(a, b, c \in K\) be distinct scalars. Let \(\phi_{a}, \phi_{b}, \phi_{c}\) be the linear functionals defined by \(\phi_{a}(f(t))=f(a), \phi_{b}(f(t))=f(b), \phi_{c}(f(t))=f(c) .\) Show that \(\left\\{\phi_{a}, \phi_{b}, \phi_{c}\right\\}\) is linearly independent, and find the basis \(\left\\{f_{1}(t), f_{2}(t), f_{3}(t)\right\\}\) of \(V\) that is its dual.
Let \(\phi\) be the linear functional on \(\mathbf{R}^{2}\) defined by \(\phi(x, y)=3 x-2 y .\) For each of the following linear mappings \(T: \mathbf{R}^{3} \rightarrow \mathbf{R}^{2},\) find \(\left(T^{t}(\phi)\right)(x, y, z)\) (a) \(T(x, y, z)=(x+y, y+z)\) (b) \(T(x, y, z)=(x+y+z, \quad 2 x-y)\)
Let \(W\) be a subspace of \(V\). For any linear functional \(\phi\) on \(W\), show that there is a linear functional \(\sigma\) on \(V\) such that \(\sigma(w)=\phi(w)\) for any \(w \in W ;\) that is, \(\phi\) is the restriction of \(\sigma\) to \(W\).
Show that (a) For any subset \(S\) of \(V, S \subseteq S^{00}\). (b) If \(S_{1} \subseteq S_{2}\), then \(S_{2}^{0} \subseteq S_{1}^{0}\).
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