Theorem subidd

Description: Subtraction of a number from itself. (Contributed by Mario Carneiro, 27-May-2016)

	Ref	Expression
Hypothesis	negidd.1	$$⊢\phi \to A\in ℂ$$
Assertion	subidd	$$⊢\phi \to A-A=0$$

Proof

Step	Hyp	Ref	Expression
1		negidd.1	$$⊢\phi \to A\in ℂ$$
2		subid	$$⊢A\in ℂ\to A-A=0$$
3	1 2	syl	$$⊢\phi \to A-A=0$$