• Support PF! Buy your school textbooks, materials and every day products Here!

Linear Algebra Help

  • Thread starter maximade
  • Start date
  • #1
27
0

Homework Statement


There are two questions in my problem set that are giving me a hard time:
1. The cross product of two vectors in R^3 is defined by [a1, a2, a3]X[b1, b2, b3]=[a2b3-a3b2, a3b1-a1b3, a1b2-a2b1] (they are all one column) Consider an arbitrary vector v in R^3. Is the transformation T(x)=VxX from r^3 to R^3 linear? If so, find its matrix in terms of the components of the vector v.
2. Find matrices of the linear transformations from R^3 to R^3:
The rotation about the y-axis through an angle theta, clockwise as viewed from the positive y-axis.


Homework Equations





The Attempt at a Solution


1. In this one I pretty much crossed v and x to get [v2x3-v3x2, v3x1-v1x3, v1x2-v2x1] after this I'm not too sure. I also only know that it is linear if the x matrix is scaled. (I think I'm wrong about that) I pretty sure it would help if I know what "linear" mean in this context.
2. A little question about the wording, is it saying that it is reflected about the y axis? If so would it be [-1 0 0, 0 1 0, 0 0 -1]?

Thanks in advance.
 

Answers and Replies

  • #2
HallsofIvy
Science Advisor
Homework Helper
41,833
955
"Linear" means that T(u+ w)= T(u)+ T(w) and that T(au= aT(u) where u and w are vectors and a is a number.

Is [itex](\vec{u}+ \vec{w})\times\vec{v}= \vec{u}\times\vec{v}+ \vec{w}\vec{v}[/itex]? Is [itex](a\vec{u})\times\vec{v}= a(\vec{u}\times\vec{v})[/itex]?
 

Related Threads on Linear Algebra Help

  • Last Post
Replies
4
Views
977
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
11
Views
883
  • Last Post
Replies
3
Views
909
  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
9
Views
1K
  • Last Post
Replies
1
Views
802
  • Last Post
Replies
1
Views
648
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
4
Views
1K
Top