Questions tagged [linear-independence]
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176 questions
3 votes
0 answers
78 views
Finding the degree $d$ of the minimal polynomial of $A$ by finding a vector $X$ such that $X,AX,\ldots,A^{d-1}X$ are linearly independent
Let $A$ be an $n \times n$ matrix over a field $F$. Let $d(A)$ be the largest non-negative integer such that the matrices $Id, A, A^2,\ldots,A^{d(A)}$ are linearly independent in the vector space of ...
4 votes
2 answers
172 views
Compute $\int\left(5\cos^3(t)-6\cos^4(t)+5\cos^5(t)-12\cos^6(t)\right)\,\mathrm{d}t$ using some results in Linear Algebra
This problem appears in the book: Linear Algebra and its applications - David C. Lay - Fourth Edition It appears in: Chapter 4 (Vector Spaces), Section 4.7 (Change of Basis), Exercise 18 $(4.7), \...
2 votes
2 answers
77 views
Proof of $\dim U^0=\dim V−\dim U$
This is an "exercise" from Linear Algebra Done Right. I'm trying to prove the following theorem using the approach outlined by the author: (3.125). Suppose $V$ is a finite-dimensional ...
5 votes
2 answers
331 views
Let $\left \{u_1, u_2, u_3, v_1, v_2, v_3 \right \}$ be vectors in $\mathbb{R}^4$. Let $U$ be the span of $\left \{u_1, u_2, u_3 \right \}$
Let $\left \{u_1, u_2, u_3, v_1, v_2, v_3 \right \}$ be vectors in $\mathbb{R}^4$. Let $U$ be the span of $\left \{u_1, u_2, u_3 \right \}$ and let $V$ be the span of $\left \{v_1, v_2, v_3 \right \}$ ...
2 votes
1 answer
70 views
Efficiently finding out which vectors from some set are linearly independent of the other vectors in the set
I have a set $S = \{v_1, v_2, \cdots, v_N\}$ with $N$ vectors, each of which have $d$ dimensions. I would now like to find a set $S' = \{n | v_n \in \mathrm{span(}S \setminus \{v_n \}) \}$, i.e. the ...
0 votes
2 answers
73 views
Linear dependency of 4 vectors in 3D space
Suppose we have 3 vectors $(a, b, c)$ in the x-y plane and a fourth $(d)$ in the y-z plane. If 4 vectors in 3D space are always linearly dependent, how do we express the fourth in terms of the other 3?...
4 votes
4 answers
365 views
Find the largest possible number of linearly independent vectors among a given set of vectors
From the book, Linear Algebra by Kuldeep Singh. Miscellaneous Exercise $2,$ Question $2.8:$ Find the largest possible number of linearly independent vectors among $v_1=\begin{bmatrix} 1 \cr -1 \cr 0 \...
2 votes
3 answers
140 views
Show that a vector $v_j$ is in the span of $w_1, \dots, w_j$ for each $j = 1, \dots, n$
I've been trying to get my head around this simple exercise question from an old linear algebra exam, but I can't find a good intuition that would help me to solve it. Suppose that $V$ is a vector ...
1 vote
1 answer
76 views
Find basis/dimension of piecewise defined polynomial vector space
Let's assume we have a piece-wise definition of polynomials, e.g. $p:[0,n]\to\mathbb{R}$ where $n\in\mathbb{N}$ and $$ \begin{align*} p(x):=\begin{cases}p_1(x):=a_1\cdot 1+b_1\cdot x+c_1\cdot x^2,&...
3 votes
1 answer
114 views
Dimension of polynomial spline space
Let be $[a,b]$ an interval and $\Delta$ a partition of $[a,b]$ where $a=\xi_0<\xi_1<\dotsc<\xi_n=b$ and $I_j:=(\xi_{j-1},\xi_j)$. Further, let be $l,m\in\mathbb{N}$. We define the space of ...
0 votes
1 answer
61 views
Conjecture about $\Bbb{C}$-linear independence of functions which are certain sums of the standard exponential functions.
Fix $M, N \in \Bbb{N}$ and define: $$ f_n(x) = \sum_{r = 0}^{MN!}{MN! \choose r} \exp\left(\frac{i2\pi rx}{n}\right), \ n = 1,\ldots,N $$ Conjecture. Then is the set $\{f_n(x), n =1,\ldots,N\}$ a $\...
1 vote
1 answer
47 views
If a finite set of functions $G_k = \{ g_n^k : n = 1..N\}$ is linearly indepdent on a real interval $I$, then so is $\lim_{k \to\infty} G_k$?
Consider the set $G_k = \{ g_n^k(x) = \cos^{2k}(\frac{2\pi h(x)}{n}) : n = 1..N\}$ where $h(x) \in \Bbb{Z}[x]$ is a polynomial such that for each $k\geq 1$, $G_k$ is a $\Bbb{R}$-linearly independent ...
2 votes
1 answer
96 views
Linear independence of subset that maps to linearly independent subset for linear map
In Peter Szekeres's "A Course in Modern Mathematical Physics", problem 3.8 on page 80 asks: Let $V$ and $W$ be any vector spaces, which are possibly infinite dimensional, and $T : V \to W$ ...
1 vote
1 answer
91 views
Linear Independence of tensor Products of Vectors
Let $m\in\mathbb{N}$ and let $x_i\in \mathbb{R}^3\setminus\{0\}$ for all $i=1,\ldots,m$. Is there any necessary and sufficient condition on $\{x_i:i=1,\ldots,m\}$, for the set $\{x^i \otimes x^i:i,\...
1 vote
1 answer
68 views
Wronskian; null space equals the span of linearly independent functions
This is an exercise from Linear Algebra by Friedberg et al. I couldn't find any related questions, so here it goes. Let $y_1,y_2,\ldots,y_n$ be linearly independent functions in $C^\infty(\mathbb C)$ ...