@epostma 

I'm sorry! I think I did something wrong. everything works as it should! Glory to maple

maple 2023 still has this error! What are we paying such money for?

@Ronan 

Interesting!

why does everything work like this? no logic at all. 

why does expand work?

Once again, Maple breaks off and does strange things. interesting in new versions the same?

@nm 

this is the elementary equation for the solution. Wolf alpha gives the answer immediately and correctly.

@Никол 

the correct answer is 0 and 1.411..

@Nikol

 0,

1.41145

@nm this is the wrong answer???????

I hope everything works more obviously in the new maples.

Digits := 30/ 

everything works out.

Maple 2020 upsets me

@Nikol 

the main problem is the complexity of the function f. it is considered very long for 256 by 256. It is the calculation itself that is long.
as an example
, if for example to build plot3d(f,...) then it takes about 20 seconds for 800 points.

@Carl Love 

Thanks/ I would like to use in the best scenario nonlinear case/

A*f(B*x,C*y). Scale parameter

@mmcdara 

I use the term copula in the sense of the term pattern.  A template that can be used with scale and offset options.

@mmcdara

Any procedure that gives two numbers x and y a third z is a function.  It matters what procedure it is.  It must be unambiguous.  What's inside the procedure (x, y) -> z is not important.

@mmcdara

There is 2D spectrum as histogram. 256 x 256 channels. I fit the two-dimensional spectrum with the function f(x, y) := Lowess(mas,fitorder=2,bandwidth=0.07). Now I've got a function f. Next step I try use NonlinearFit(a*f(x, y), mas2, [a],... ). Apparently the function f is considered very slowly.  And my procedure can't issue a solution, it just freeze