English
Translation by a fixed vector preserves segment membership: a ∈ [x -[𝕜] y] implies a + translation belongs to [a+y -[𝕜] a+z] iff x ∈ [y -[𝕜] z].
Русский
Сдвиг на фиксированный вектор сохраняет принадлежность к сегменту: a ∈ [x -[𝕜] y] ⇔ ...
LaTeX
$$$$ a ∈ [x -[\mathbb{K}] y] \iff a \in [x -[\mathbb{K}] y]. $$$$
Lean4
@[simp]
theorem mem_segment_translate (a : E) {x b c} : a + x ∈ [a + b -[𝕜] a + c] ↔ x ∈ [b -[𝕜] c] := by
simp_rw [← vadd_eq_add, ← vadd_segment, vadd_mem_vadd_set_iff]