Theorem iuneq1

Description: Equality theorem for indexed union. (Contributed by NM, 27-Jun-1998)

	Ref	Expression
Assertion	iuneq1	⊢ ( 𝐴 = 𝐵 → ∪ 𝑥 ∈ 𝐴 𝐶 = ∪ 𝑥 ∈ 𝐵 𝐶 )

Proof

Step	Hyp	Ref	Expression
1		iunss1	⊢ ( 𝐴 ⊆ 𝐵 → ∪ 𝑥 ∈ 𝐴 𝐶 ⊆ ∪ 𝑥 ∈ 𝐵 𝐶 )
2		iunss1	⊢ ( 𝐵 ⊆ 𝐴 → ∪ 𝑥 ∈ 𝐵 𝐶 ⊆ ∪ 𝑥 ∈ 𝐴 𝐶 )
3	1 2	anim12i	⊢ ( ( 𝐴 ⊆ 𝐵 ∧ 𝐵 ⊆ 𝐴 ) → ( ∪ 𝑥 ∈ 𝐴 𝐶 ⊆ ∪ 𝑥 ∈ 𝐵 𝐶 ∧ ∪ 𝑥 ∈ 𝐵 𝐶 ⊆ ∪ 𝑥 ∈ 𝐴 𝐶 ) )
4		eqss	⊢ ( 𝐴 = 𝐵 ↔ ( 𝐴 ⊆ 𝐵 ∧ 𝐵 ⊆ 𝐴 ) )
5		eqss	⊢ ( ∪ 𝑥 ∈ 𝐴 𝐶 = ∪ 𝑥 ∈ 𝐵 𝐶 ↔ ( ∪ 𝑥 ∈ 𝐴 𝐶 ⊆ ∪ 𝑥 ∈ 𝐵 𝐶 ∧ ∪ 𝑥 ∈ 𝐵 𝐶 ⊆ ∪ 𝑥 ∈ 𝐴 𝐶 ) )
6	3 4 5	3imtr4i	⊢ ( 𝐴 = 𝐵 → ∪ 𝑥 ∈ 𝐴 𝐶 = ∪ 𝑥 ∈ 𝐵 𝐶 )