Step |
Hyp |
Ref |
Expression |
1 |
|
ltadd2 |
⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐴 ∈ ℝ ) → ( 𝐴 < 𝐵 ↔ ( 𝐴 + 𝐴 ) < ( 𝐴 + 𝐵 ) ) ) |
2 |
1
|
3anidm13 |
⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → ( 𝐴 < 𝐵 ↔ ( 𝐴 + 𝐴 ) < ( 𝐴 + 𝐵 ) ) ) |
3 |
|
simpl |
⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → 𝐴 ∈ ℝ ) |
4 |
3
|
recnd |
⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → 𝐴 ∈ ℂ ) |
5 |
|
times2 |
⊢ ( 𝐴 ∈ ℂ → ( 𝐴 · 2 ) = ( 𝐴 + 𝐴 ) ) |
6 |
4 5
|
syl |
⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → ( 𝐴 · 2 ) = ( 𝐴 + 𝐴 ) ) |
7 |
6
|
breq1d |
⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → ( ( 𝐴 · 2 ) < ( 𝐴 + 𝐵 ) ↔ ( 𝐴 + 𝐴 ) < ( 𝐴 + 𝐵 ) ) ) |
8 |
|
readdcl |
⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → ( 𝐴 + 𝐵 ) ∈ ℝ ) |
9 |
|
2re |
⊢ 2 ∈ ℝ |
10 |
|
2pos |
⊢ 0 < 2 |
11 |
9 10
|
pm3.2i |
⊢ ( 2 ∈ ℝ ∧ 0 < 2 ) |
12 |
11
|
a1i |
⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → ( 2 ∈ ℝ ∧ 0 < 2 ) ) |
13 |
|
ltmuldiv |
⊢ ( ( 𝐴 ∈ ℝ ∧ ( 𝐴 + 𝐵 ) ∈ ℝ ∧ ( 2 ∈ ℝ ∧ 0 < 2 ) ) → ( ( 𝐴 · 2 ) < ( 𝐴 + 𝐵 ) ↔ 𝐴 < ( ( 𝐴 + 𝐵 ) / 2 ) ) ) |
14 |
3 8 12 13
|
syl3anc |
⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → ( ( 𝐴 · 2 ) < ( 𝐴 + 𝐵 ) ↔ 𝐴 < ( ( 𝐴 + 𝐵 ) / 2 ) ) ) |
15 |
2 7 14
|
3bitr2d |
⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → ( 𝐴 < 𝐵 ↔ 𝐴 < ( ( 𝐴 + 𝐵 ) / 2 ) ) ) |