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Metamath Proof Explorer

Theorem xnegnegd

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

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

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