EDB — 26S

Exercises

1. [26S]Let \(X\) be an ordinal and

   \[ P_ x =\{ z\in X, z\in x\} \]

   show that

   \[ ∀ x,y∈ X~ ,~ P_ x = P_ y ⇒ x=y\quad . \]
   Solution 1

   [26T]↺↻

   (Note the similarity with [271]↺↻).