Prove Derivative Matrices Mapping F:Rn→Rm is Ax+c

In summary, the problem states that if the mapping F:Rn\rightarrowRm is continuously differentiable and has a fixed mxn matrix A as its derivative, then F(x)=Ax+c for some constant c\inRm. The solution involves using the first-order approximation and identifying c explicitly by multiplying A with the vector (x-xo).
  • #1
Appa
15
0

Homework Statement


Suppose that the mapping F:Rn[tex]\rightarrow[/tex]Rm is continuously differentiable and that there is a fixed mxn matrix A so that
DF(x)=A for every x in Rn.

Prove that then F is a mapping such that F(x)=Ax+c for some c[tex]\in[/tex]Rm

Homework Equations



DF(x)ij= [tex]\partial[/tex]Fi(x)/[tex]\partial[/tex]xj (the ijth entry of the derivative matrix)

The Attempt at a Solution


I tried to solve this with the first-order approximation F(x)=F(xo)+F´(xo)(x-xo) +[tex]\epsilon[/tex](x-xo)||x-xo||

Where [tex]\epsilon[/tex](x-xo)||x-xo|| approaches naught.
But it didn't amount to anything sensible and I'm not sure what to do... What should I try next?
 
Physics news on Phys.org
  • #2
Appa said:
I tried to solve this with the first-order approximation F(x)=F(xo)+F´(xo)(x-xo) +[tex]\epsilon[/tex](x-xo)||x-xo||

Actually, when you write F´(xo)(x-xo) like in a Taylor series, you mean
DF(xo) . (x-xo)
which is a multiplication of a matrix by a vector. You know that DF(xo) = A... if your expansion is otherwise correct that should enable you to actually identify c explicitly.
 

1. What does it mean for a derivative matrix to map from Rn to Rm?

The derivative matrix of a function is a matrix that represents the rate of change of the function at a given point. When the derivative matrix maps from Rn to Rm, it means that the function is taking n-dimensional input variables and producing m-dimensional output variables.

2. How do you prove that a derivative matrix maps from Rn to Rm?

To prove that a derivative matrix maps from Rn to Rm, you need to show that the matrix has n rows and m columns, indicating that it takes n-dimensional input and produces m-dimensional output. Additionally, the entries in the matrix should correspond to the partial derivatives of the function with respect to each input variable.

3. What is the role of A and c in the statement "Ax+c" when proving a derivative matrix maps from Rn to Rm?

The letter A in "Ax+c" represents the derivative matrix, while c is a constant vector. These two components help to define the linear transformation that the function is performing. The A matrix determines the rate of change of the function, while c represents any constant shifts in the output variables.

4. Why is it important to prove that a derivative matrix maps from Rn to Rm?

Proving that a derivative matrix maps from Rn to Rm is important because it provides evidence that the function is continuously differentiable. This means that the function has a well-defined rate of change at every point, which is a crucial concept in calculus and optimization problems.

5. How can you use the "Ax+c" statement to simplify the process of proving a derivative matrix maps from Rn to Rm?

The "Ax+c" statement can be used to simplify the process of proving a derivative matrix maps from Rn to Rm by breaking down the function into smaller, more manageable parts. The A matrix represents the linear transformation of the function, while the c vector represents any constant shifts. By breaking down the function in this way, it is easier to calculate the partial derivatives and prove that the derivative matrix maps from Rn to Rm.

Similar threads

  • Calculus and Beyond Homework Help
Replies
12
Views
2K
  • Calculus and Beyond Homework Help
Replies
1
Views
2K
  • Calculus and Beyond Homework Help
Replies
6
Views
1K
  • Calculus and Beyond Homework Help
Replies
8
Views
2K
  • Calculus and Beyond Homework Help
Replies
7
Views
1K
Replies
5
Views
1K
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
5
Views
5K
  • Linear and Abstract Algebra
Replies
6
Views
772
  • Calculus and Beyond Homework Help
Replies
2
Views
1K
Back
Top