Theorem xnegnegi

Description: Extended real version of negneg . (Contributed by Glauco Siliprandi, 2-Jan-2022)

	Ref	Expression
Hypothesis	xnegnegi.1	$$⊢A\in {ℝ}^{*}$$
Assertion	xnegnegi	$$⊢-\left(-A\right)=A$$

Proof

Step	Hyp	Ref	Expression
1		xnegnegi.1	$$⊢A\in {ℝ}^{*}$$
2		xnegneg	$$⊢A\in {ℝ}^{*}\to -\left(-A\right)=A$$
3	1 2	ax-mp	$$⊢-\left(-A\right)=A$$