Linear transformation 2 x 2 matrix problem

In summary, the conversation discusses finding a 2x2 matrix that maps e1 to -e2 and e2 to e1+3e2. The solution involves starting with a general matrix and identifying the elements that will satisfy both conditions. The final matrix is 0 1, -1 3.
  • #1
SYoungblood
64
1

Homework Statement


[/B]
Find a 2 x 2 matrix that maps e1 to –e2 and e2 to e1+3e2

Homework Equations


[/B]
See the above notes

The Attempt at a Solution


[/B]
I am making a pig's ear out of this one.

I think I can get e1 to –e2

3 -1

1 -3

but as far as getting it to reconcile a matrix like the above to match both conditions is kicking my posterior.

Thanks much for your help

SY
 
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  • #2
The matrix you quote does not map e1 to -e2. I recommend that you start by writing down the most general matrix and then see how it acts on e1 and e2 respectively. From there you can identify the elements of the matrix.
 
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  • #3
Orodruin said:
The matrix you quote does not map e1 to -e2. I recommend that you start by writing down the most general matrix and then see how it acts on e1 and e2 respectively. From there you can identify the elements of the matrix.

Here's a simple 2x2 mattrix --
0 1

-1 0
So, if I multiply that by [1 over 0], I get 1 * [0 over -1} + 0 [1 over 0] = [0 over -1].

Multiplying by our T vector [1 over 0], e1has become -e2 by taking the former e2 and basically multiplying this by -1 and turning it upside down.

I am having problems wrapping my mind around this one and I am trying to break it down Barney style.
 
  • #4
I think I got it

0 1

1 3

Am I in the ballpark?

SY
 
  • #5
In the ballpark, yes. That matrix maps e1 to e2 and e2 to e1+3e2, ie, you are missing a minus sign in the mapping of e1.
 
  • #6
Aha.

0 1

-1 3

To use your tag line, a child of five might understand this, but I am not a child of five.
 
  • #7
Yes, that is correct.

SYoungblood said:
To use your tag line, a child of five might understand this, but I am not a child of five.
I would lend you my niece, but she turned six the day before yesterday. ;)
 
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  • #8
Geez, now that I have the answer, it is amazing how easy this question was.

Thank you very much for your help, I greatly appreciate it.

SY
 

Related to Linear transformation 2 x 2 matrix problem

1. What is a linear transformation?

A linear transformation is a mathematical operation that maps one vector space to another while preserving the basic structure of the original space. In simpler terms, it is a transformation that maintains the lines and origin of a graph.

2. What is a 2 x 2 matrix?

A 2 x 2 matrix is a mathematical notation used to represent a set of numbers arranged in a rectangular array of two rows and two columns. It is often used to represent linear transformations in two-dimensional space.

3. How do you perform a linear transformation on a 2 x 2 matrix?

To perform a linear transformation on a 2 x 2 matrix, you need to multiply the matrix by a transformation matrix, which contains the coefficients of the transformation. The resulting matrix will represent the new coordinates of each point after the transformation.

4. What are some common applications of linear transformations in 2 x 2 matrices?

Linear transformations in 2 x 2 matrices have various applications in fields such as computer graphics, image processing, and physics. They can be used to rotate, scale, reflect, or shear objects in a two-dimensional space.

5. How do you determine if a linear transformation in a 2 x 2 matrix is invertible?

A linear transformation in a 2 x 2 matrix is invertible if its determinant is non-zero. The determinant can be calculated by multiplying the elements in the main diagonal and subtracting the product of the elements in the other diagonal. If the determinant is zero, the transformation is not invertible.

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