English
Let R be a relation R: α → β → Prop. If β is empty, then BiTotal R is equivalent to α being empty.
Русский
Пусть R — отношение α → β → Prop. Если β пусто, BiTotal(R) эквивалентно пустоте α.
LaTeX
$$$ [\operatorname{IsEmpty}(\beta)] \Rightarrow \big( \operatorname{BiTotal}(R) \iff \operatorname{IsEmpty}(\alpha) \big) $$$
Lean4
theorem biTotal_iff_isEmpty_left [IsEmpty β] : BiTotal R ↔ IsEmpty α := by
simp only [BiTotal, leftTotal_iff_isEmpty_left, rightTotal_empty, and_true]