How do you prove that the curves of y=x^x and y = the Functional Continued Fraction (FCF) generated by y=x^(x(1+1/y)) touch y=x, at their common point ( 1, 1 )?

1 Answer
Aug 27, 2016

The curves intersect without osculating.

Explanation:

Considering

y=x^(x(1+1/y)) equiv y^(y/(y+1))-x^x we have

f_1(x,y)= y^(y/(y+1))-x^x = 0 and
f_2(x,y)=y-x^x=0

Those functions intersect at clearly at {x = 1,y=1}. This can be verified by simple substitution.

Now the tangency at this point obeys

((dy)/(dx))_1 = -(f_1)_x/((f_1)_y) = ( (1 + y)^2 (1 + Log_e(x)))/(1 + y + Log_e(y)) = 2
((dy)/(dx))_2 = -(f_2)_x/((f_2)_y) =x^x (1 + Log_e(x)) = 1

So they intersect without osculating.