Theorem difss

Description: Subclass relationship for class difference. Exercise 14 of TakeutiZaring p. 22. (Contributed by NM, 29-Apr-1994)

	Ref	Expression
Assertion	difss	$$⊢A\setminus B\subseteq A$$

Proof

Step	Hyp	Ref	Expression
1		eldifi	$$⊢x\in \left(A\setminus B\right)\to x\in A$$
2	1	ssriv	$$⊢A\setminus B\subseteq A$$