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Metamath Proof Explorer

Theorem sqrtlt

Description: Square root is strictly monotonic. Closed form of sqrtlti . (Contributed by Scott Fenton, 17-Apr-2014) (Proof shortened by Mario Carneiro, 29-May-2016)

Ref Expression
Assertion sqrtlt ( ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ∧ ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ) → ( 𝐴 < 𝐵 ↔ ( √ ‘ 𝐴 ) < ( √ ‘ 𝐵 ) ) )

Proof

Step Hyp Ref Expression
1 sqrtle ⊢ ( ( ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ∧ ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ) → ( 𝐵 ≤ 𝐴 ↔ ( √ ‘ 𝐵 ) ≤ ( √ ‘ 𝐴 ) ) )
2 1 ancoms ⊢ ( ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ∧ ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ) → ( 𝐵 ≤ 𝐴 ↔ ( √ ‘ 𝐵 ) ≤ ( √ ‘ 𝐴 ) ) )
3 2 notbid ⊢ ( ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ∧ ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ) → ( ¬ 𝐵 ≤ 𝐴 ↔ ¬ ( √ ‘ 𝐵 ) ≤ ( √ ‘ 𝐴 ) ) )
4 simpll ⊢ ( ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ∧ ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ) → 𝐴 ∈ ℝ )
5 simprl ⊢ ( ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ∧ ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ) → 𝐵 ∈ ℝ )
6 4 5 ltnled ⊢ ( ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ∧ ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ) → ( 𝐴 < 𝐵 ↔ ¬ 𝐵 ≤ 𝐴 ) )
7 resqrtcl ⊢ ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) → ( √ ‘ 𝐴 ) ∈ ℝ )
8 7 adantr ⊢ ( ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ∧ ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ) → ( √ ‘ 𝐴 ) ∈ ℝ )
9 resqrtcl ⊢ ( ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) → ( √ ‘ 𝐵 ) ∈ ℝ )
10 9 adantl ⊢ ( ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ∧ ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ) → ( √ ‘ 𝐵 ) ∈ ℝ )
11 8 10 ltnled ⊢ ( ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ∧ ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ) → ( ( √ ‘ 𝐴 ) < ( √ ‘ 𝐵 ) ↔ ¬ ( √ ‘ 𝐵 ) ≤ ( √ ‘ 𝐴 ) ) )
12 3 6 11 3bitr4d ⊢ ( ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) ∧ ( 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵 ) ) → ( 𝐴 < 𝐵 ↔ ( √ ‘ 𝐴 ) < ( √ ‘ 𝐵 ) ) )