What is the basis for the subspace W spanned by {sin^2(x), cos^2(x), cos2x}?

In summary, the subspace W of C[0,1] spanned by S={sin^2(x),cos^2(x),cos2x} does not have a basis because S is not linearly independent. To find a basis for W, we can use trig identities to express one function in terms of the others and see which function is superfluous. In this case, any two of the functions in S will form a basis for W.
  • #1
physicsss
319
0
I'm stumped by this problem:

let W be the subspace of C[0,1] spanned by S={sin^2(x),cos^2(x),cos2x}

a) explain why S is not a basis for W

it's because S not linearly independent

b) find a basis for W

please help me with this one...

TIA.
 
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  • #2
physicsss said:
I'm stumped by this problem:

let W be the subspace of C[0,1] spanned by S={sin^2(x),cos^2(x),cos2x}

a) explain why S is not a basis for W

it's because S not linearly independent

b) find a basis for W

please help me with this one...

TIA.
This one is easy think about trig identities and try to express one function in terms of the others. See which function is superfluous.
 
  • #3
show each one is superfluous.
 
  • #4
Oh..sorry for the confusion. I just needed help with b). I already know how to do a).
 
  • #5
and they answered b for you. they span a space of fewer then 3 dimensions, so it's 0,1 or 2, but obviously 0 or 1 is nonsense so you just need to find two of them that aer independent. as mathwonk says any two will do.
 

1. What is subspace base math?

Subspace base math is a mathematical concept used in linear algebra to solve problems related to vector spaces. It involves finding a set of vectors that can span the entire space and form a basis for the subspace.

2. How is subspace base math used in real life?

Subspace base math has many applications in fields such as physics, engineering, and computer science. It is used to solve problems involving systems of linear equations, to analyze data sets, and to design algorithms for computer graphics and machine learning.

3. What is the process for finding a subspace base?

The first step in finding a subspace base is to determine the dimension of the subspace. This can be done by finding the number of linearly independent vectors in the subspace. Then, a set of linearly independent vectors that span the subspace can be found using methods such as Gaussian elimination or the Gram-Schmidt process.

4. How do you represent a subspace base mathematically?

A subspace base can be represented as a matrix, with each column representing a vector in the subspace. Alternatively, it can be represented using a set of coefficients for each vector, such as in a linear combination.

5. What are the advantages of using subspace base math?

Subspace base math allows for the efficient and accurate solving of problems involving vector spaces. It also provides a powerful tool for analyzing and manipulating data. Additionally, it has many practical applications in various fields, making it a valuable skill for scientists and engineers.

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