Expectation value for a spin-half particle.

[hhhmortal]

Homework Statement

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

Homework Equations

The Attempt at a Solution

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

 

[gabbagabbahey]

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