Theorem: evenpow_neg (ECTate/Algebra/Ring/Basic.lean)

State before:
R : Type u_1
inst✝ : CommRing R
n m : ℕ
a : R
h : n = 2 * m
⊢ (-a) ^ n = a ^ n
Tactic:
rw [h, pow_mul, pow_mul, neg_sq]
State after:
no goals