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bjgawp
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I'm going through Axler's book and just got introduced the concept of sums of subspaces and the direct sums.
Here's one of the examples he has.
Now the other examples he had were kind of trivial (such as [tex]\mathbb{R}^2 = U \oplus W[/tex] where [tex]U = \{ (x,0) | x \in \mathbb{R} \}[/tex] and [tex]W = \{(0,y) | y \in \mathbb{R} \}[/tex]) since we simply showed the uniqueness of each component.
For this one, I get rattled up in notation and not sure where to head. Here's what I was thinking
let [tex]q \in U_e + Uo[/tex]. Then: [tex]q(x) = \underbrace{a_0 + a_2 x^2 + \cdots + a_{2n}x^{2n}}_{\in U_e} + \underbrace{a_1x + a_3x^3 + \cdots a_{2n+1}x^{2n+1}}_{\in U_o}[/tex]
Then I assume [tex]a(x)[/tex] can be represented by different coefficients, say [tex]b_0, b_1, ..., b_n[/tex]. Since both these representations are equal to [tex]a(x)[/tex], then the two representations are equal. Then we equate the coefficients and we arrive at a contradiction.
Sound good? Sorry for the long winded post. I appreciate all the help so far! (And that last thread .. that was pretty silly of me to mess up!)
Here's one of the examples he has.
Let [tex]P(F)[/tex] denote all polynomials with coefficients in [tex]F[/tex] where F is a field.
Let [tex]U_e[/tex] denote the subspace of [tex]P(F)[/tex] consisting of all polynomials of the form [tex]p(z) = \sum_{i=0}^n a_{2i}z^{2i}[/tex]
and let [tex]U_o[/tex] denote the subspace of P(F) consisting of all polynomials [tex]p[/tex] of the form: [tex]p(z) =
\sum_{i=0}^{n} a_{2i+1}z^{2i+1}[/tex]
You should verify that [tex]P(F) = U_e \oplus U_o[/tex]
Now the other examples he had were kind of trivial (such as [tex]\mathbb{R}^2 = U \oplus W[/tex] where [tex]U = \{ (x,0) | x \in \mathbb{R} \}[/tex] and [tex]W = \{(0,y) | y \in \mathbb{R} \}[/tex]) since we simply showed the uniqueness of each component.
For this one, I get rattled up in notation and not sure where to head. Here's what I was thinking
let [tex]q \in U_e + Uo[/tex]. Then: [tex]q(x) = \underbrace{a_0 + a_2 x^2 + \cdots + a_{2n}x^{2n}}_{\in U_e} + \underbrace{a_1x + a_3x^3 + \cdots a_{2n+1}x^{2n+1}}_{\in U_o}[/tex]
Then I assume [tex]a(x)[/tex] can be represented by different coefficients, say [tex]b_0, b_1, ..., b_n[/tex]. Since both these representations are equal to [tex]a(x)[/tex], then the two representations are equal. Then we equate the coefficients and we arrive at a contradiction.
Sound good? Sorry for the long winded post. I appreciate all the help so far! (And that last thread .. that was pretty silly of me to mess up!)