Theorem neg1sqe1

Description: -u 1 squared is 1. (Contributed by David A. Wheeler, 8-Dec-2018)

	Ref	Expression
Assertion	neg1sqe1	⊢ ( - 1 ↑ 2 ) = 1

Proof

Step	Hyp	Ref	Expression
1		ax-1cn	⊢ 1 ∈ ℂ
2		sqneg	⊢ ( 1 ∈ ℂ → ( - 1 ↑ 2 ) = ( 1 ↑ 2 ) )
3	1 2	ax-mp	⊢ ( - 1 ↑ 2 ) = ( 1 ↑ 2 )
4		sq1	⊢ ( 1 ↑ 2 ) = 1
5	3 4	eqtri	⊢ ( - 1 ↑ 2 ) = 1