Suppose, ?, y and z are three basic independent variables.
x is a variable which is a linear function of ?.
p is another variable which is a function of ? and z, but not y, and the expression of p in terms of ? and z is not known.
How to write them in sequence?
What will be the results of D[p, ?], D[p, y] and D[p, z]?
x = a*\[Theta]
p = pf[\[Theta], z]