Theorem enpr1g

Description: { A , A } has only one element. (Contributed by FL, 15-Feb-2010)

	Ref	Expression
Assertion	enpr1g	$$⊢A\in V\to \left\{A,A\right\}\approx 1_{𝑜}$$

Proof

Step	Hyp	Ref	Expression
1		dfsn2	$$⊢\left\{A\right\}=\left\{A,A\right\}$$
2		ensn1g	$$⊢A\in V\to \left\{A\right\}\approx 1_{𝑜}$$
3	1 2	eqbrtrrid	$$⊢A\in V\to \left\{A,A\right\}\approx 1_{𝑜}$$