Theorem ex-2nd

Description: Example for df-2nd . Example by David A. Wheeler. (Contributed by Mario Carneiro, 18-Jun-2015)

	Ref	Expression
Assertion	ex-2nd	⊢ ( 2nd ‘ ⟨ 3 , 4 ⟩ ) = 4

Proof

Step	Hyp	Ref	Expression
1		3ex	⊢ 3 ∈ V
2		4re	⊢ 4 ∈ ℝ
3	2	elexi	⊢ 4 ∈ V
4	1 3	op2nd	⊢ ( 2nd ‘ ⟨ 3 , 4 ⟩ ) = 4