THEOREM 9.5. Let X be a Hilbert space and let A: X₁, X₂, ... be an orthonormal set in X. Then, if EF (n = 1, 2, ...), we have (1) Σ1%* converges if and only if Σ=₁ |α₂|² < ∞, and (2) if Σ₁%,* converges to x, then α = (x, xn). =1 Proof (2). Consider makking from *x to F x = 2 an n=1 S₂ = 24x₁. α; = (Sn, xj). Since this relationship is true (that is, the value remains the same) for any n> j, it must also be true in the limit, and we can write and the partial sum For n>j, we define Request explain the underlined parts Thm 9.2 это Xis an lim(S₁, xj) = αj. n mer product space, Appealing to Theorem 9.2, we can assert the continuity of the inner product mapping which allows us to interchange the operations of limit and inner product e inver product in the above equation, which yields _n,Y) is a continuous (x, xj) = αj, which is the desired result. Thus, knowing that the given series converges to some x, we have a strong relationship between the coefficients in the series and x.
THEOREM 9.5. Let X be a Hilbert space and let A: X₁, X₂, ... be an orthonormal set in X. Then, if EF (n = 1, 2, ...), we have (1) Σ1%* converges if and only if Σ=₁ |α₂|² < ∞, and (2) if Σ₁%,* converges to x, then α = (x, xn). =1 Proof (2). Consider makking from *x to F x = 2 an n=1 S₂ = 24x₁. α; = (Sn, xj). Since this relationship is true (that is, the value remains the same) for any n> j, it must also be true in the limit, and we can write and the partial sum For n>j, we define Request explain the underlined parts Thm 9.2 это Xis an lim(S₁, xj) = αj. n mer product space, Appealing to Theorem 9.2, we can assert the continuity of the inner product mapping which allows us to interchange the operations of limit and inner product e inver product in the above equation, which yields _n,Y) is a continuous (x, xj) = αj, which is the desired result. Thus, knowing that the given series converges to some x, we have a strong relationship between the coefficients in the series and x.
Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter10: Sequences, Series, And Probability
Section: Chapter Questions
Problem 63RE
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