Also, you can't assume that 0.9 = 1 in this proof. I don't remember the exact reason (maybe someone here does), but proving that 1.9 = 2 is like proving that 0.9 = 1 so you can't use the 0.9 = 1 assumption.
EDIT: Heh, as I was searching the web for 1.9 =/!= 2 info, I found the proof that you are using above.
