# Very very very easy quantum exam question

1. Jan 22, 2005

### chrismuktar

I know this is an easy question but I want to confirm that I've got this right.

The wavefunction $$\psi(r)$$ can be expressed as a linear sum of orthonormal eigenfunctions $$\phi_n(r)$$ by

$$\psi(r) = \sum a_n\phi_n(r)$$.

Derive an expression for the coefficients $$a_n$$.

I think the answer is $$a_n = <\phi_n|\psi>$$ but this seems a little too easy.

Opinions?
Thanks,
C.

2. Jan 22, 2005

### vincentchan

you are correct.....