Metamath Proof Explorer

Theorem iooltub

Description: An element of an open interval is less than its upper bound. (Contributed by Glauco Siliprandi, 11-Dec-2019)

Ref Expression
Assertion iooltub ⊢ A ∈ ℝ * ∧ B ∈ ℝ * ∧ C ∈ A B → C < B

Proof

Step Hyp Ref Expression
1 elioo2 ⊢ A ∈ ℝ * ∧ B ∈ ℝ * → C ∈ A B ↔ C ∈ ℝ ∧ A < C ∧ C < B
2 simp3 ⊢ C ∈ ℝ ∧ A < C ∧ C < B → C < B
3 1 2 syl6bi ⊢ A ∈ ℝ * ∧ B ∈ ℝ * → C ∈ A B → C < B
4 3 3impia ⊢ A ∈ ℝ * ∧ B ∈ ℝ * ∧ C ∈ A B → C < B