Expectation value for a spin-half particle.

1. Nov 12, 2009

hhhmortal

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

Calculate the expectation value of the operator $$_{}Sz$$ for a spin-half particle known to be in an eigenstate of the operator $$_{}Sz$$

2. Relevant equations

3. The attempt at a solution

I know the eigenvalues for the $$_{}Sz$$ but how can I find the expectation values from this?

2. Nov 12, 2009

gabbagabbahey

You might start with the definition of expectation value (in equation form)....