Theorem sq9

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

	Ref	Expression
Assertion	sq9	$$⊢9^2=81$$

Proof

Step	Hyp	Ref	Expression
1		9cn	$$⊢9\in ℂ$$
2	1	sqvali	$$⊢9^2=9\cdot 9$$
3		9t9e81	$$⊢9\cdot 9=81$$
4	2 3	eqtri	$$⊢9^2=81$$