(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

http://img168.imageshack.us/img168/5042/48390466ny3.png [Broken]

2. Relevant equations

A orthonormal system is if [tex] f_i \cdot f_j = 0[/tex] for all [tex]i \neq j[/tex] and if [tex]||f_i||=1[/tex]

A sequence contained in [tex]l^{\infty}[/tex] is a bounded sequence.

http://img99.imageshack.us/img99/1840/67874379ps9.png [Broken]

3. The attempt at a solution

My guess is that I have to use theorem 9.3 but I don't understand the notation. <x,e_n> is x just a number?

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# Homework Help: Hilbert space

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