13 lines
543 B
Text
13 lines
543 B
Text
module
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axiom A : Type
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axiom angle (x y z : A) : Int
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axiom pi : Int
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axiom Collinear (x y z : A) : Prop
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axiom collinear_iff_eq_or_eq_or_angle_eq_zero_or_angle_eq_pi {p₁ p₂ p₃ : A} :
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Collinear p₁ p₂ p₃ ↔ p₁ = p₂ ∨ p₃ = p₂ ∨ angle p₁ p₂ p₃ = 0 ∨ angle p₁ p₂ p₃ = pi
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example {a b c a' b' c' : A} (h : ¬Collinear a b c)
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(ha₁ : angle a b c = angle a' b' c')
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(h' : angle a' b' c' = 0 ∨ angle a' b' c' = pi) :
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False := by
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grind only [collinear_iff_eq_or_eq_or_angle_eq_zero_or_angle_eq_pi]
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