# Expectation value problem

Discussion in 'Math' started by boks, Nov 16, 2008.

1. ### boks Thread Starter Active Member

Oct 10, 2008
218
0
1. The problem statement, all variables and given/known data

Calculate $\Delta x = \sqrt{\left\langle(x - \left\langle x \right\rangle )^2 \right\rangle}$ if $\left\langle x \right\rangle = 0$ and $\left\langle x^2 \right\rangle = a^2(\frac{\pi - 6}{12 \pi^2})$

2. The attempt at a solution

$\left\langle(x - \left\langle x \right\rangle )^2 \right\rangle = \left\langle x^2 - 2x \left\langle x \right\rangle + \left\langle x \right\rangle ^2 \right\rangle$

How can I proceed here?

2. ### steveb Senior Member

Jul 3, 2008
2,433
469
Wouldn't the next logical step be to take advantage of the fact that $\left\langle x \right\rangle = 0$ ?

The problem looks a whole lot simpler once you do that.

3. ### boks Thread Starter Active Member

Oct 10, 2008
218
0
Lol, stupid of me.