# Is this a typo?

1. Nov 15, 2009

### Void123

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

In my textbook, the formula for the expectation value is written as:

$$<x> = \int \Psi^{*}\Psi dx$$

Shouldn't there be an $$x$$ next to $$|\Psi|^{2}$$ ?

Thanks.

2. Relevant equations

3. The attempt at a solution

2. Nov 15, 2009

### short circut

yes it should read

$$<x>=<\psi|x|\psi> = \int_{-\infty}^{\infty}\psi^*x\psi dx$$

make sure you write it in this form too. Otherwise when you start putting in other operators like p you will get it wrong.