Theorem xnegnegd

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

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

Proof

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