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theorem proved term proof

add_contains_add

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formal statement (Lean)

  57theorem add_contains_add {x y : ℝ} {I J : Interval}
  58    (hx : I.contains x) (hy : J.contains y) : (I + J).contains (x + y) := by

proof body

Term-mode proof.

  59  constructor
  60  · simp only [add_lo, Rat.cast_add]
  61    exact add_le_add hx.1 hy.1
  62  · simp only [add_hi, Rat.cast_add]
  63    exact add_le_add hx.2 hy.2
  64
  65/-- Negation of intervals: -[a,b] = [-b, -a] -/

used by (2)

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depends on (11)

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