First of all , I would like to apologize for not understanding how to install " TamperMonkey " ( for typing mathematical symbols ) . I am completely and utterly ignorant when it comes to Information Technology and Computin 😢

Therefore , I apologize if I violate any rules here on this subreddit .

I will use the symbols from a keyboard that I downloaded for my Android device .

CONTEXT FOR MY QUESTION

Suppose I have 6 variables and a functional relationship U between them ( 5 independent and 1 dependent ) :

- Independent Variables : s , t , x , y , z ;

- Dependent Variable : u ;

Thus , this functional relationship can be written as

U : ℝ⁵ → ℝ¹ with u = U ( s , t , x , y , z )

Now , suppose that the variables x , y are each dependent on s , t , that is ,

x = X ( s , t ) with X : ℝ² → ℝ¹

y = Y ( s , t ) with Y : ℝ² → ℝ¹

Therefore , the functional relation U becomes a functional relation Û , with the dependent variable u being dependent , via Û , only on s , t , z .…