rename testgame to adam

2023-03-23 17:10:13 +01:00
parent a262cff63b
commit 5c73d3bddb
166 changed files with 0 additions and 0 deletions
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+import Mathlib.Tactic.Ring
+import Mathlib.Algebra.BigOperators.Fin
+
+open BigOperators
+
+lemma arithmetic_sum (n : ℕ) : 2 * (∑ i : Fin (n + 1), ↑i) = n * (n + 1) := by
+  induction' n with n hn
+  simp
+  rw [Fin.sum_univ_castSucc]
+  rw [mul_add]
+  simp
+  rw [mul_add, hn]
+  simp_rw [Nat.succ_eq_one_add]
+  ring