bookshelf/FirstCourseAbstractAlgebra/Chapter1.lean

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/-
Chapter 1
Introduction and Examples
-/
import Mathlib.Data.Complex.Basic
open Complex
open HPow
-- In Exercises 1 through 9 compute the given arithmetic expression and give the
-- answer in the form $a + bi$ for $a, b ∈ $.
theorem ex1_1 : I^3 = 0 + (-1) * I := calc
I^3
= I * (I * hPow I 1) := rfl
_ = 0 + (-1) * I := by simp