5 lines
156 B
Text
5 lines
156 B
Text
variables A : Type
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example (s₁ s₂ s₃ : set A) : s₁ ⊆ s₂ → s₂ ⊆ s₃ → s₁ ⊆ s₃ :=
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assume h₁ h₂ a ains₁,
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h₂ (h₁ ains₁)
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