Theorem eldifad

Description: If a class is in the difference of two classes, it is also in the minuend. One-way deduction form of eldif . (Contributed by David Moews, 1-May-2017)

	Ref	Expression
Hypothesis	eldifad.1	⊢ ( 𝜑 → 𝐴 ∈ ( 𝐵 ∖ 𝐶 ) )
Assertion	eldifad	⊢ ( 𝜑 → 𝐴 ∈ 𝐵 )

Proof

Step	Hyp	Ref	Expression
1		eldifad.1	⊢ ( 𝜑 → 𝐴 ∈ ( 𝐵 ∖ 𝐶 ) )
2		eldif	⊢ ( 𝐴 ∈ ( 𝐵 ∖ 𝐶 ) ↔ ( 𝐴 ∈ 𝐵 ∧ ¬ 𝐴 ∈ 𝐶 ) )
3	1 2	sylib	⊢ ( 𝜑 → ( 𝐴 ∈ 𝐵 ∧ ¬ 𝐴 ∈ 𝐶 ) )
4	3	simpld	⊢ ( 𝜑 → 𝐴 ∈ 𝐵 )