Theorem subidi

Description: Subtraction of a number from itself. (Contributed by NM, 26-Nov-1994)

	Ref	Expression
Hypothesis	negidi.1	$$⊢A\in ℂ$$
Assertion	subidi	$$⊢A-A=0$$

Proof

Step	Hyp	Ref	Expression
1		negidi.1	$$⊢A\in ℂ$$
2		subid	$$⊢A\in ℂ\to A-A=0$$
3	1 2	ax-mp	$$⊢A-A=0$$