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Theorem del-size-02

⊦ a ∈ s ∧ a ≠ b → #(s -- b -- a) = #(s -- b) - 1

Type: A user defined theorem
Validity: The proof is valid.
Features: simp, localsimp,
Comment:
Used by: del-three-01,
Used by units in proved state:
Proof exists?: Yes

View the proof

Infos about the proof

Proved?: Yes
Interactions: 0
Proof steps: 4
Used lemmas: del-in-01, del-in, del-size,
Used spec theorems:
- Used simplifier rules:
  - set-basic/size-zero-01
  - set-basic/ne-01