Proof of Theorem sinhalfpilem
| Step | Hyp | Ref
 | Expression | 
| 1 |   | sq1 10725 | 
. . . 4
⊢
(1↑2) = 1 | 
| 2 |   | pire 15022 | 
. . . . . . . . . . . . . . . . 17
⊢ π
∈ ℝ | 
| 3 | 2 | recni 8038 | 
. . . . . . . . . . . . . . . 16
⊢ π
∈ ℂ | 
| 4 |   | 2cn 9061 | 
. . . . . . . . . . . . . . . 16
⊢ 2 ∈
ℂ | 
| 5 |   | 2ap0 9083 | 
. . . . . . . . . . . . . . . 16
⊢ 2 #
0 | 
| 6 | 3, 4, 5 | divcanap2i 8782 | 
. . . . . . . . . . . . . . 15
⊢ (2
· (π / 2)) = π | 
| 7 | 6 | fveq2i 5561 | 
. . . . . . . . . . . . . 14
⊢
(sin‘(2 · (π / 2))) = (sin‘π) | 
| 8 | 2 | rehalfcli 9240 | 
. . . . . . . . . . . . . . . 16
⊢ (π /
2) ∈ ℝ | 
| 9 | 8 | recni 8038 | 
. . . . . . . . . . . . . . 15
⊢ (π /
2) ∈ ℂ | 
| 10 |   | sin2t 11914 | 
. . . . . . . . . . . . . . 15
⊢ ((π /
2) ∈ ℂ → (sin‘(2 · (π / 2))) = (2 ·
((sin‘(π / 2)) · (cos‘(π / 2))))) | 
| 11 | 9, 10 | ax-mp 5 | 
. . . . . . . . . . . . . 14
⊢
(sin‘(2 · (π / 2))) = (2 · ((sin‘(π /
2)) · (cos‘(π / 2)))) | 
| 12 | 7, 11 | eqtr3i 2219 | 
. . . . . . . . . . . . 13
⊢
(sin‘π) = (2 · ((sin‘(π / 2)) ·
(cos‘(π / 2)))) | 
| 13 |   | sinpi 15021 | 
. . . . . . . . . . . . 13
⊢
(sin‘π) = 0 | 
| 14 | 12, 13 | eqtr3i 2219 | 
. . . . . . . . . . . 12
⊢ (2
· ((sin‘(π / 2)) · (cos‘(π / 2)))) =
0 | 
| 15 |   | 0cn 8018 | 
. . . . . . . . . . . . 13
⊢ 0 ∈
ℂ | 
| 16 |   | sincl 11871 | 
. . . . . . . . . . . . . . 15
⊢ ((π /
2) ∈ ℂ → (sin‘(π / 2)) ∈
ℂ) | 
| 17 | 9, 16 | ax-mp 5 | 
. . . . . . . . . . . . . 14
⊢
(sin‘(π / 2)) ∈ ℂ | 
| 18 |   | coscl 11872 | 
. . . . . . . . . . . . . . 15
⊢ ((π /
2) ∈ ℂ → (cos‘(π / 2)) ∈
ℂ) | 
| 19 | 9, 18 | ax-mp 5 | 
. . . . . . . . . . . . . 14
⊢
(cos‘(π / 2)) ∈ ℂ | 
| 20 | 17, 19 | mulcli 8031 | 
. . . . . . . . . . . . 13
⊢
((sin‘(π / 2)) · (cos‘(π / 2))) ∈
ℂ | 
| 21 | 15, 4, 20, 5 | divmulapi 8793 | 
. . . . . . . . . . . 12
⊢ ((0 / 2)
= ((sin‘(π / 2)) · (cos‘(π / 2))) ↔ (2 ·
((sin‘(π / 2)) · (cos‘(π / 2)))) = 0) | 
| 22 | 14, 21 | mpbir 146 | 
. . . . . . . . . . 11
⊢ (0 / 2) =
((sin‘(π / 2)) · (cos‘(π / 2))) | 
| 23 | 4, 5 | div0api 8773 | 
. . . . . . . . . . 11
⊢ (0 / 2) =
0 | 
| 24 | 22, 23 | eqtr3i 2219 | 
. . . . . . . . . 10
⊢
((sin‘(π / 2)) · (cos‘(π / 2))) =
0 | 
| 25 |   | resincl 11885 | 
. . . . . . . . . . . . 13
⊢ ((π /
2) ∈ ℝ → (sin‘(π / 2)) ∈
ℝ) | 
| 26 | 8, 25 | ax-mp 5 | 
. . . . . . . . . . . 12
⊢
(sin‘(π / 2)) ∈ ℝ | 
| 27 |   | 2re 9060 | 
. . . . . . . . . . . . . . 15
⊢ 2 ∈
ℝ | 
| 28 |   | pipos 15024 | 
. . . . . . . . . . . . . . 15
⊢ 0 <
π | 
| 29 |   | 2pos 9081 | 
. . . . . . . . . . . . . . 15
⊢ 0 <
2 | 
| 30 | 2, 27, 28, 29 | divgt0ii 8946 | 
. . . . . . . . . . . . . 14
⊢ 0 <
(π / 2) | 
| 31 |   | 4re 9067 | 
. . . . . . . . . . . . . . . 16
⊢ 4 ∈
ℝ | 
| 32 |   | pigt2lt4 15020 | 
. . . . . . . . . . . . . . . . 17
⊢ (2 <
π ∧ π < 4) | 
| 33 | 32 | simpri 113 | 
. . . . . . . . . . . . . . . 16
⊢ π <
4 | 
| 34 | 2, 31, 33 | ltleii 8129 | 
. . . . . . . . . . . . . . 15
⊢ π ≤
4 | 
| 35 | 27, 29 | pm3.2i 272 | 
. . . . . . . . . . . . . . . . 17
⊢ (2 ∈
ℝ ∧ 0 < 2) | 
| 36 |   | ledivmul 8904 | 
. . . . . . . . . . . . . . . . 17
⊢ ((π
∈ ℝ ∧ 2 ∈ ℝ ∧ (2 ∈ ℝ ∧ 0 < 2))
→ ((π / 2) ≤ 2 ↔ π ≤ (2 · 2))) | 
| 37 | 2, 27, 35, 36 | mp3an 1348 | 
. . . . . . . . . . . . . . . 16
⊢ ((π /
2) ≤ 2 ↔ π ≤ (2 · 2)) | 
| 38 |   | 2t2e4 9145 | 
. . . . . . . . . . . . . . . . 17
⊢ (2
· 2) = 4 | 
| 39 | 38 | breq2i 4041 | 
. . . . . . . . . . . . . . . 16
⊢ (π
≤ (2 · 2) ↔ π ≤ 4) | 
| 40 | 37, 39 | bitr2i 185 | 
. . . . . . . . . . . . . . 15
⊢ (π
≤ 4 ↔ (π / 2) ≤ 2) | 
| 41 | 34, 40 | mpbi 145 | 
. . . . . . . . . . . . . 14
⊢ (π /
2) ≤ 2 | 
| 42 |   | 0xr 8073 | 
. . . . . . . . . . . . . . 15
⊢ 0 ∈
ℝ* | 
| 43 |   | elioc2 10011 | 
. . . . . . . . . . . . . . 15
⊢ ((0
∈ ℝ* ∧ 2 ∈ ℝ) → ((π / 2) ∈
(0(,]2) ↔ ((π / 2) ∈ ℝ ∧ 0 < (π / 2) ∧ (π /
2) ≤ 2))) | 
| 44 | 42, 27, 43 | mp2an 426 | 
. . . . . . . . . . . . . 14
⊢ ((π /
2) ∈ (0(,]2) ↔ ((π / 2) ∈ ℝ ∧ 0 < (π / 2)
∧ (π / 2) ≤ 2)) | 
| 45 | 8, 30, 41, 44 | mpbir3an 1181 | 
. . . . . . . . . . . . 13
⊢ (π /
2) ∈ (0(,]2) | 
| 46 |   | sin02gt0 11929 | 
. . . . . . . . . . . . 13
⊢ ((π /
2) ∈ (0(,]2) → 0 < (sin‘(π / 2))) | 
| 47 | 45, 46 | ax-mp 5 | 
. . . . . . . . . . . 12
⊢ 0 <
(sin‘(π / 2)) | 
| 48 | 26, 47 | gt0ap0ii 8655 | 
. . . . . . . . . . 11
⊢
(sin‘(π / 2)) # 0 | 
| 49 | 15, 17, 19, 48 | divmulapi 8793 | 
. . . . . . . . . 10
⊢ ((0 /
(sin‘(π / 2))) = (cos‘(π / 2)) ↔ ((sin‘(π / 2))
· (cos‘(π / 2))) = 0) | 
| 50 | 24, 49 | mpbir 146 | 
. . . . . . . . 9
⊢ (0 /
(sin‘(π / 2))) = (cos‘(π / 2)) | 
| 51 | 17, 48 | div0api 8773 | 
. . . . . . . . 9
⊢ (0 /
(sin‘(π / 2))) = 0 | 
| 52 | 50, 51 | eqtr3i 2219 | 
. . . . . . . 8
⊢
(cos‘(π / 2)) = 0 | 
| 53 | 52 | oveq1i 5932 | 
. . . . . . 7
⊢
((cos‘(π / 2))↑2) = (0↑2) | 
| 54 |   | sq0 10722 | 
. . . . . . 7
⊢
(0↑2) = 0 | 
| 55 | 53, 54 | eqtri 2217 | 
. . . . . 6
⊢
((cos‘(π / 2))↑2) = 0 | 
| 56 | 55 | oveq2i 5933 | 
. . . . 5
⊢
(((sin‘(π / 2))↑2) + ((cos‘(π / 2))↑2)) =
(((sin‘(π / 2))↑2) + 0) | 
| 57 |   | sincossq 11913 | 
. . . . . 6
⊢ ((π /
2) ∈ ℂ → (((sin‘(π / 2))↑2) + ((cos‘(π /
2))↑2)) = 1) | 
| 58 | 9, 57 | ax-mp 5 | 
. . . . 5
⊢
(((sin‘(π / 2))↑2) + ((cos‘(π / 2))↑2)) =
1 | 
| 59 | 56, 58 | eqtr3i 2219 | 
. . . 4
⊢
(((sin‘(π / 2))↑2) + 0) = 1 | 
| 60 | 17 | sqcli 10712 | 
. . . . 5
⊢
((sin‘(π / 2))↑2) ∈ ℂ | 
| 61 | 60 | addridi 8168 | 
. . . 4
⊢
(((sin‘(π / 2))↑2) + 0) = ((sin‘(π /
2))↑2) | 
| 62 | 1, 59, 61 | 3eqtr2ri 2224 | 
. . 3
⊢
((sin‘(π / 2))↑2) = (1↑2) | 
| 63 |   | 0re 8026 | 
. . . . 5
⊢ 0 ∈
ℝ | 
| 64 | 63, 26, 47 | ltleii 8129 | 
. . . 4
⊢ 0 ≤
(sin‘(π / 2)) | 
| 65 |   | 1re 8025 | 
. . . 4
⊢ 1 ∈
ℝ | 
| 66 |   | 0le1 8508 | 
. . . 4
⊢ 0 ≤
1 | 
| 67 |   | sq11 10704 | 
. . . 4
⊢
((((sin‘(π / 2)) ∈ ℝ ∧ 0 ≤ (sin‘(π /
2))) ∧ (1 ∈ ℝ ∧ 0 ≤ 1)) → (((sin‘(π /
2))↑2) = (1↑2) ↔ (sin‘(π / 2)) = 1)) | 
| 68 | 26, 64, 65, 66, 67 | mp4an 427 | 
. . 3
⊢
(((sin‘(π / 2))↑2) = (1↑2) ↔ (sin‘(π /
2)) = 1) | 
| 69 | 62, 68 | mpbi 145 | 
. 2
⊢
(sin‘(π / 2)) = 1 | 
| 70 | 69, 52 | pm3.2i 272 | 
1
⊢
((sin‘(π / 2)) = 1 ∧ (cos‘(π / 2)) =
0) |