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gibson:teaching:fall-2016:iam961:hw1 [2016/09/02 08:25] gibson |
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**1.** Prove that any linear map $\mathcal{L} : \mathbb{C}^n \rightarrow \mathbb{C}^m$ can | **1.** Prove that any linear map $\mathcal{L} : \mathbb{C}^n \rightarrow \mathbb{C}^m$ can | ||
- | written as an $m \times n$ matrix. (Hint: let $y = \mathcal{L}(x)$. Express $x$ as a linear combination of the canonical basis vectors $\{e_j\}$. Substitute that into $y = \mathcal{L}(x)$, then use linearity to rewrite the right-hand-side of this equation as a linear combination of vectors $\mathcal{L}(e_j)$. Now take the inner product of both sides of this equation with $e_i$. That should give you $y_i = \sum_j=1^n L_{ij} x_j$ for some matrix $L$.) | + | written as an $m \times n$ matrix. (Hint: let $y = \mathcal{L}(x)$. Express $x$ as a linear combination of the canonical basis vectors $\{e_j\}$. Substitute that into $y = \mathcal{L}(x)$, then use linearity to rewrite the right-hand-side of this equation as a linear combination of vectors $\mathcal{L}(e_j)$. Now take the inner product of both sides of this equation with $e_i$. That should give you $y_i = \sum_{j=1}^n L_{ij} x_j$ for some matrix $L$.) |
**2.** Prove that $\|A B \|_p \leq \|A\|_p \|B\|_p$. | **2.** Prove that $\|A B \|_p \leq \|A\|_p \|B\|_p$. |