Can a Basis for a Subspace Always Include Specific Elements of a Larger Basis?

In summary: If so, then you can add that vector to your basis for W to get a basis for V. This ensures that every vector in V can be written as a linear combination of elements from your basis.In summary, for any subspace W of a finite dimensional inner product space V, we can find a basis for W that includes m elements of a basis for V, and we can also extend any basis for W to a basis for V.
  • #1
ehsan_thr
3
0
suppose that {ei} 1<=i<=n is a basis for v and w is a subspace of v of dimension m<n ... . so Can we always find a basis for w which includes m elements of {ei} 1<=i<=n ?

does always w include m elements of {ei} 1<=i<=n ?
 
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  • #2
What does it mean for a list of vectors to be the basis for a vector space V ?
 
  • #3
It means ,every vector of v is a linear combination of elements of the basis ... . ( The elements of v must be linear independent )
I have tried to prove my question , but i coudn't till now ... . my ultimate goal is to prove that for Every proper subspace W of a finite dimensional inner product space V there is a non zero vector x which is orothogonal to w ... .
 
  • #4
ehsan_thr said:
suppose that {ei} 1<=i<=n is a basis for v and w is a subspace of v of dimension m<n ... . so Can we always find a basis for w which includes m elements of {ei} 1<=i<=n ?

does always w include m elements of {ei} 1<=i<=n ?

No. For example, let v be the set of linear polynomials and let {ei}= {x- 1, x+ 1}. Let w be the set of all multiples of x. Then w is a one dimensional subspace of v and any basis for w must be {ax} for some non-zero number a. None of those is in {ei}.

The other way is true: given any basis for subspace w we can extend it to a basis for v.
 
  • #5
No. For example, let v be the set of linear polynomials and let {ei}= {x- 1, x+ 1}. Let w be the set of all multiples of x. Then w is a one dimensional subspace of v and any basis for w must be {ax} for some non-zero number a. None of those is in {ei}.

The other way is true: given any basis for subspace w we can extend it to a basis for v.
T 01:59 PM

Thank you , so much , i will find another solution for my problem ... .
 
  • #6
Here's how I might approach the problem:

Start with an orthogonal basis of W, and pick any vector v in V that's not in W. Using your basis for W, can you use v to find a vector that's orthogonal to W?
 

What is the basis of subspace?

The basis of subspace is a set of vectors that span the entire subspace and are linearly independent, meaning none of the vectors can be expressed as a linear combination of the others.

Why is the basis of subspace important?

The basis of subspace is important because it allows us to represent any vector within the subspace using a linear combination of the basis vectors. This makes it easier to manipulate and understand the vectors within the subspace.

How do you find the basis of subspace?

To find the basis of subspace, you can use the process of elimination to determine which vectors are linearly independent. Another method is to use the Gram-Schmidt process, which involves orthogonalizing a set of vectors to obtain a basis.

Can a subspace have more than one basis?

Yes, a subspace can have multiple bases. However, all bases for a given subspace will have the same number of vectors, known as the dimension of the subspace.

What is the relationship between the basis of subspace and the dimension of the subspace?

The number of vectors in the basis of a subspace is equal to the dimension of the subspace. This means that the basis is a minimal set of vectors needed to span the entire subspace.

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