Now outputs would become inputs and inputs outputs if we are to get values, but solution is just formula of that curve but in YX... In other words when you look it all just in XY, there is formula and curve and there should be formula for curve symetrical to function y=x... Shouldn't AutoCAD be capable of getting that curve function, or even there shouldn't even be need for getting formula - there is initial formula and corresponding Y^-1 (but no need for that - just normal Y function of curve is enough), so for every y coordinate there is x one read diractly from that curve...

It's only possible if the function is bijective, that means for each x there is only one y and vice-versa. Linear functions are like this.

So you know the f(x) function (not really the expression of the function, but only it's output) and you want to solve the x in y=f(x) .

Plot the function as spline with (x, f(x)) points and draw a horizontal Xline at (0,y,0). If you are lucky and it intersect the plot, the inverse is the x coordinate of the intersection.

Of course, the spline is finite, from a,f(a) to b,f(b). If it doesn't intersect, change the interval.