Theorem mulm1d

Description: Product with minus one is negative. (Contributed by Mario Carneiro, 27-May-2016)

	Ref	Expression
Hypothesis	mulm1d.1	$$⊢\phi \to A\in ℂ$$
Assertion	mulm1d	$$⊢\phi \to -1A=-A$$

Proof

Step	Hyp	Ref	Expression
1		mulm1d.1	$$⊢\phi \to A\in ℂ$$
2		mulm1	$$⊢A\in ℂ\to -1A=-A$$
3	1 2	syl	$$⊢\phi \to -1A=-A$$