Theorem sq9

Description: The square of 9 is 81. (Contributed by SN, 30-Mar-2025)

	Ref	Expression
Assertion	sq9	|- ( 9 ^ 2 ) = ; 8 1

Proof

Step	Hyp	Ref	Expression
1		9cn	|- 9 e. CC
2	1	sqvali	|- ( 9 ^ 2 ) = ( 9 x. 9 )
3		9t9e81	|- ( 9 x. 9 ) = ; 8 1
4	2 3	eqtri	|- ( 9 ^ 2 ) = ; 8 1