According to this page, Edward's curve point doubling can be represented in a different way by assuming $c=1$ and $d = r^2$.
It then says we can represent $x y$ as $Y Z$ satisfying $r\cdot y = \frac Y Z$
I am a bit confused. How would I then calculate the $x$ coordinate? For example, they have provided the following explicit formula:
YY = Y12 ZZ = r*Z12 V = s*(ZZ-YY)2 W = (ZZ+YY)2 Y3 = W-V Z3 = W+V
So after obtaining $Y_3$ and $Z_3$, how would I revert back to affine coordinates and calculate $x$ and $y$?