I'm trying to study for exams and can't get a hold of my professor. Anyway, I'm trying to figure out a problem regarding spin. You're given two particles of different spin and the S^2 is measured. It asks for the possible values you could measure, but wouldn't that just be the eigenvalues defined by S^2|sm>=hbar^2*s(s+1)|sm>? That just seems too easy. (edit: I realized what to do on this part...I was just being stupid. I'm still having trouble with the second part). And for the second part, you're given the result after measuring the total S(z) and the S(z) of one of the particles. It then asks for what possible values you could get for S^2 and their probabilities. But, and I'm probably misunderstanding the question, isn't the result going to still be s*(s+1), which, considering the spins haven't changed, wouldn't have changed?