Theorem xnegcld

Description: Closure of extended real negative. (Contributed by Mario Carneiro, 28-May-2016)

	Ref	Expression
Hypothesis	xnegcld.1	$$⊢\phi \to A\in {ℝ}^{*}$$
Assertion	xnegcld	$$⊢\phi \to -A\in {ℝ}^{*}$$

Proof

Step	Hyp	Ref	Expression
1		xnegcld.1	$$⊢\phi \to A\in {ℝ}^{*}$$
2		xnegcl	$$⊢A\in {ℝ}^{*}\to -A\in {ℝ}^{*}$$
3	1 2	syl	$$⊢\phi \to -A\in {ℝ}^{*}$$