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Math 3130: Introduction to Linear Algebra, Spring 2014


Homework


Assignment
Assigned
Due
Problems
HW1 1/23/14
1/29/14
1.  Do Exercise 1.3.2.

2.  Do Exercise 2.3.2. Explain why your answer is correct.

3.  Do Exercise 3.2.1.
HW2 1/31/14
2/5/14
1.  Do Exercise 2.5.7.

2.  Do Exercise 3.5.5.

3.  Do Exercise 3.7.2.
HW3 2/6/14
2/14/14
1. 
(a) Find a right inverse of the matrix $$ \left[ \begin{array}{ccc} 1&2&3\\ 4&5&6 \end{array} \right] $$ or explain why none exists.
(b) Find a left inverse of $$ \left[ \begin{array}{cc} 1&2\\ 2&4\\ 3&6 \end{array} \right] $$ or explain why none exists.

2. 
(a) Show that the set of functions $\{x,x+1,x+2\}$ is linearly dependent.
(b) Show that the set of functions $\{1,\sin^2(x),\cos^2(x)\}$ is linearly dependent.

3.  For $A\in M_{m\times n}(\mathbb R)$, show that the solution set of $A{\bf x}={\bf 0}$ is a subspace of $\mathbb R^n$.
HW4 2/15/14
2/21/14
1.  Do Exercise 4.1.1 parts (a), (b), (c). (For each part, say whether the set is a subspace, then give a very brief justification for your answer.)

2.  Do Exercises 4.3.2 and 4.3.7.

3.  Do Exercise 4.4.1.
HW5 2/19/14
2/26/14
1.  Do Exercise 4.2.1, except replace the phrase "spanning sets" with "bases".

2.  Do Exercises 4.2.3 and 4.2.5.

3.  Do Exercise 4.2.6(a)(b).
HW6 3/5/14
3/12/14
1.  Do Exercise 4.7.8.

2.  Do Exercises 4.7.12(a) and 4.7.13.

3.  Do Exercise 4.7.18.
HW7 3/12/14
3/19/14
1.  Do Exercise 4.8.1.

2.  Do Exercises 4.8.2 and 4.8.9.

3.  Do Exercises 4.8.3 and 4.8.4. (Note: for 4.8.3(b), the matrix $Q$ should be ${}_{\mathcal S}[\textrm{id}]_{{\mathcal S}'}$.)
HW8 3/19/14
4/2/14
1.  Do this network flow problem.

2.  Balance the equation $B_2S_3+H_2O\to H_3BO_3+H_2S$.

3.  Consider the production model ${\bf x}=C{\bf x}+{\bf d}$ for an economy with two sectors where $C=\left[\begin{array}{cc}.2&.5\\.6&.1\end{array}\right]$ and ${\bf d}=\left[\begin{array}{cc}16\\12\end{array}\right]$. Solve for the equilibirum production level.
HW9 4/3/14
4/9/14
1.  Do Exercise 5.1.2(a)(b). Also, determine
(c) the unit vectors in the directions of ${\bf u}$ and ${\bf v}$, and
(d) the angle between ${\bf u}$ and ${\bf v}$.

2.  
(a) Find a vector that is orthogonal to both ${\bf u}=\left[\begin{array}{c}0\\1\\1\end{array}\right]$ and ${\bf v}=\left[\begin{array}{c}1\\0\\1\end{array}\right]$.
(b) The points $\left[\begin{array}{c}0\\0\\0\end{array}\right]$, $\left[\begin{array}{c}0\\1\\1\end{array}\right]$, $\left[\begin{array}{c}1\\0\\1\end{array}\right]$ and $\left[\begin{array}{c}1\\1\\0\end{array}\right]$ are the vertices of a regular tetrahedron. Find vectors orthogonal to two adjacent faces.
(c) Find the angle between two adjacent faces of a regular tetrahedron.

3.   Let $V = \mathbb P_2(t)$. Explain why the function $$ \langle f,g\rangle:=\int_0^1 f(t)g(t)\;dt$$ is an inner product on $V$.
HW10 4/9/14
4/16/14
1.  Let $V = M_{m\times n}(\mathbb C)$. Explain why the function $$ \langle A,B\rangle = \textrm{trace}(A^H\cdot B) = \textrm{trace}(A^*\cdot B) $$ is a complex inner product on $V$.

2.  Do Exercise 5.4.1(a)(b)(c)(d)

3.  Let $A$ be an $m\times n$ real matrix. Show that the null space of $A$ is the orthogonal complement of the row space, and the left null space is the orthogonal complement of the column space. How are the dimensions of all of these spaces related?
HW11
Last one!
4/18/14
4/23/14
1.  Do Exercise 5.5.2.

2.  Do Exercise 5.6.8.

3.  Do Exercise 5.13.12.