Math Problem Statement

Determine if the vectors v1=[0,0,2], v2=[0,5,1], v3=[2,1,-8] are linearly independent. Solve other problems such as eigenvalues of a 2x2 matrix, cross products, projections, and checking if vectors are coplanar.

Solution

Let's break down the tasks and solve each problem step by step:


1. Determine if the vectors v1=[0,0,2]\mathbf{v_1} = [0, 0, 2], v2=[0,5,1]\mathbf{v_2} = [0, 5, 1], v3=[2,1,8]\mathbf{v_3} = [2, 1, -8] are linearly independent.

To determine linear independence:

  • Form a matrix MM where each column is one of the vectors: 0 & 0 & 2 \\ 0 & 5 & 1 \\ 2 & 1 & -8 \end{bmatrix}.$$
  • Calculate the determinant of MM. If the determinant is non-zero, the vectors are linearly independent.

2. If a=i+2j\mathbf{a} = i + 2j, b=ki\mathbf{b} = k - i, and c=a+2b\mathbf{c} = a + 2b, find c×(ab)\mathbf{c} \times (\mathbf{a} - \mathbf{b}).

Steps:

  1. Compute ab\mathbf{a} - \mathbf{b}.
  2. Compute c\mathbf{c} using the given relation.
  3. Take the cross product c×(ab)\mathbf{c} \times (\mathbf{a} - \mathbf{b}).

3. Find all eigenvalues and corresponding eigenvectors for the matrix A=[2145]A = \begin{bmatrix} 2 & 1 \\ 4 & 5 \end{bmatrix}.

Steps:

  1. Solve det(AλI)=0\det(A - \lambda I) = 0 to find the eigenvalues (λ\lambda).
  2. Substitute each eigenvalue back into (AλI)v=0(A - \lambda I)\mathbf{v} = 0 to find the eigenvectors.

4. Let v=(1,3)\mathbf{v} = (1, 3) and w=(4,2)\mathbf{w} = (-4, -2). Write v\mathbf{v} as the sum of two orthogonal vectors, one of which is the projection of v\mathbf{v} onto w\mathbf{w}.

Steps:

  1. Compute the projection of v\mathbf{v} onto w\mathbf{w}: projwv=vwwww.\text{proj}_{\mathbf{w}} \mathbf{v} = \frac{\mathbf{v} \cdot \mathbf{w}}{\mathbf{w} \cdot \mathbf{w}} \mathbf{w}.
  2. Subtract this projection from v\mathbf{v} to find the orthogonal vector: v=projwv+orthogonal component.\mathbf{v} = \text{proj}_{\mathbf{w}} \mathbf{v} + \text{orthogonal component}.

5. Are the vectors u=(8,4,1)\mathbf{u} = (8, -4, 1), v=(3,2,5)\mathbf{v} = (3, -2, 5), and w=(13,6,3)\mathbf{w} = (-13, 6, 3) in the same plane?

To check if the vectors are coplanar:

  • Form a matrix with these vectors as rows or columns: 8 & -4 & 1 \\ 3 & -2 & 5 \\ -13 & 6 & 3 \end{bmatrix}.$$
  • Compute the determinant of MM. If the determinant is zero, the vectors are coplanar.

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Math Problem Analysis

Mathematical Concepts

Linear Algebra
Vector Spaces
Matrix Determinants
Eigenvalues and Eigenvectors
Cross Product
Orthogonal Projections
Vector Coplanarity

Formulas

Determinant of a matrix
Eigenvalue equation: det(A - λI) = 0
Cross product formula
Projection formula: proj_w(v) = (v·w / w·w)w

Theorems

Linear independence criterion (non-zero determinant)
Properties of eigenvalues and eigenvectors
Coplanarity condition (zero determinant)

Suitable Grade Level

Undergraduate Math (Linear Algebra Course)