(adsbygoogle = window.adsbygoogle || []).push({}); Ket Notation -- Effects of the Projection Operator

1. The problem statement, all variables and given/known data

From Sakurai's Modern Quantum Mechanics (Revised Edition), it is just deriving equation 1.3.12.

2. Relevant equations

[tex] \begin{eqnarray*}\langle \alpha |\cdot (\sum_{a'}^N |a'\rangle \langle a'|) \cdot|\alpha \rangle \end{eqnarray*} [/tex]

3. The attempt at a solution

The summation can be moved to the left, so everything is being summed from a' to N, but does an alpha bra inner product with a' (or <α|a'>) does the sum of this from all a' to N equal Ʃ<a'|α>? maybe this is simple and I just can't see it?

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# Homework Help: Ket Notation - Effects of the Projection Operator

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