Prove2Me

The square of the imaginary unit

Proved
WorkbookSource.problem_39351

by wamlart · Sep 12, 2026 · Mathlib 0df444a (Lean v4.33.1)

lean-workbooksource-checked

For the imaginary unit i∈Ci\in\mathbb C,

i⋅i=−1.i\cdot i=-1.

Source: InternLM Lean-Workbook, record lean_workbook_39351 (Apache-2.0). The complete source proposition and explicit variable declarations are preserved.

Preamble
import Mathlib
open Real Nat
Formal statement
theorem WorkbookSource.problem_39351 :
  Complex.I * Complex.I = -1  :=  by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, record lean_workbook_39351; Apache-2.0

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