Hi,

1. What do you mean by "derive" ? Do you mean finding in function of the other variables ? Here, it is possible, because :

, and therefore by extension it becomes

2. I don't understand but maybe this could help you :

, and therefore by extension it becomes

3. Itcouldgive rise to probability values, you could try to study this :

It is equivalent to your first equation, except is the subject, maybe you could investigate what happens to when you change , or . But I believe you will not reach a concrete result easily .