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Theorem sincos4thpi 8705
Description: The sine and cosine of pi / 4. (Contributed by Paul Chapman, 25-Jan-2008.)
Assertion
Ref Expression
sincos4thpi |- ((sin` (pi / 4)) = (1 / (sqr` 2)) /\ (cos` (pi / 4)) = (1 / (sqr` 2)))

Proof of Theorem sincos4thpi
StepHypRef Expression
1 2re 5981 . . . . . . . . . . . 12 |- 2 e. RR
2 2ne0 5992 . . . . . . . . . . . 12 |- 2 =/= 0
31, 2rereccl 5803 . . . . . . . . . . 11 |- (1 / 2) e. RR
43recn 5326 . . . . . . . . . 10 |- (1 / 2) e. CC
5 ax1cn 5281 . . . . . . . . . . 11 |- 1 e. CC
6 2halvest 6041 . . . . . . . . . . 11 |- (1 e. CC -> ((1 / 2) + (1 / 2)) = 1)
75, 6ax-mp 7 . . . . . . . . . 10 |- ((1 / 2) + (1 / 2)) = 1
8 sincosq1eq 8704 . . . . . . . . . 10 |- (((1 / 2) e. CC /\ (1 / 2) e. CC /\ ((1 / 2) + (1 / 2)) = 1) -> (sin`
((1 / 2) x. (pi / 2))) = (cos` ((1 / 2) x. (pi / 2))))
94, 4, 7, 8mp3an 918 . . . . . . . . 9 |- (sin` ((1 / 2) x. (pi / 2))) = (cos` ((1 / 2) x. (pi / 2)))
109opreq2i 3978 . . . . . . . 8 |- ((sin` ((1 / 2) x. (pi / 2))) x. (sin`
((1 / 2) x. (pi / 2)))) = ((sin`
((1 / 2) x. (pi / 2))) x. (cos` ((1 / 2) x. (pi / 2))))
1110opreq2i 3978 . . . . . . 7 |- (2 x. ((sin` ((1 / 2) x. (pi / 2))) x. (sin` ((1 / 2) x. (pi / 2))))) = (2 x. ((sin` ((1 / 2) x. (pi / 2))) x. (cos` ((1 / 2) x. (pi / 2)))))
12 2cn 5982 . . . . . . . . . . . 12 |- 2 e. CC
13 pire 8672 . . . . . . . . . . . . 13 |- pi e. RR
1413recn 5326 . . . . . . . . . . . 12 |- pi e. CC
155, 12, 14, 12, 2, 2divmuldiv 5788 . . . . . . . . . . 11 |- ((1 / 2) x. (pi / 2)) = ((1 x. pi) / (2 x. 2))
1614mulid2 5345 . . . . . . . . . . . 12 |- (1 x. pi) = pi
17 2t2e4 6024 . . . . . . . . . . . 12 |- (2 x. 2) = 4
1816, 17opreq12i 3979 . . . . . . . . . . 11 |- ((1 x. pi) / (2 x. 2)) = (pi / 4)
1915, 18eqtr 1498 . . . . . . . . . 10 |- ((1 / 2) x. (pi / 2)) = (pi / 4)
2019fveq2i 3733 . . . . . . . . 9 |- (sin` ((1 / 2) x. (pi / 2))) = (sin` (pi / 4))
2120, 20opreq12i 3979 . . . . . . . 8 |- ((sin` ((1 / 2) x. (pi / 2))) x. (sin`
((1 / 2) x. (pi / 2)))) = ((sin`
(pi / 4)) x. (sin` (pi / 4)))
2221opreq2i 3978 . . . . . . 7 |- (2 x. ((sin` ((1 / 2) x. (pi / 2))) x. (sin` ((1 / 2) x. (pi / 2))))) = (2 x. ((sin` (pi / 4)) x. (sin` (pi / 4))))
2312, 2recid 5740 . . . . . . . . . . 11 |- (2 x. (1 / 2)) = 1
2423opreq1i 3977 . . . . . . . . . 10 |- ((2 x. (1 / 2)) x. (pi / 2)) = (1 x. (pi / 2))
2513, 1, 2redivcl 5800 . . . . . . . . . . . 12 |- (pi / 2) e. RR
2625recn 5326 . . . . . . . . . . 11 |- (pi / 2) e. CC
2712, 4, 26mulass 5337 . . . . . . . . . 10 |- ((2 x. (1 / 2)) x. (pi / 2)) = (2 x. ((1 / 2) x. (pi / 2)))
2826mulid2 5345 . . . . . . . . . 10 |- (1 x. (pi / 2)) = (pi / 2)
2924, 27, 283eqtr3 1506 . . . . . . . . 9 |- (2 x. ((1 / 2) x. (pi / 2))) = (pi / 2)
3029fveq2i 3733 . . . . . . . 8 |- (sin` (2 x. ((1 / 2) x. (pi / 2)))) = (sin` (pi / 2))
314, 26mulcl 5333 . . . . . . . . 9 |- ((1 / 2) x. (pi / 2)) e. CC
32 sin2tt 7462 . . . . . . . . 9 |- (((1 / 2) x. (pi / 2)) e. CC -> (sin` (2 x. ((1 / 2) x. (pi / 2)))) = (2 x. ((sin`
((1 / 2) x. (pi / 2))) x. (cos` ((1 / 2) x. (pi / 2))))))
3331, 32ax-mp 7 . . . . . . . 8 |- (sin` (2 x. ((1 / 2) x. (pi / 2)))) = (2 x. ((sin` ((1 / 2) x. (pi / 2))) x. (cos`
((1 / 2) x. (pi / 2)))))
34 sinhalfpi 8675 . . . . . . . 8 |- (sin` (pi / 2)) = 1
3530, 33, 343eqtr3 1506 . . . . . . 7 |- (2 x. ((sin` ((1 / 2) x. (pi / 2))) x. (cos` ((1 / 2) x. (pi / 2))))) = 1
3611, 22, 353eqtr3 1506 . . . . . 6 |- (2 x. ((sin` (pi / 4)) x. (sin` (pi / 4)))) = 1
3736fveq2i 3733 . . . . 5 |- (sqr` (2 x. ((sin` (pi / 4)) x. (sin` (pi / 4))))) = (sqr` 1)
38 4re 5984 . . . . . . . . 9 |- 4 e. RR
39 4pos 5994 . . . . . . . . . 10 |- 0 < 4
4038, 39gt0ne0i 5629 . . . . . . . . 9 |- 4 =/= 0
4113, 38, 40redivcl 5800 . . . . . . . 8 |- (pi / 4) e. RR
42 resinclt 7438 . . . . . . . 8 |- ((pi / 4) e. RR -> (sin` (pi / 4)) e. RR)
4341, 42ax-mp 7 . . . . . . 7 |- (sin` (pi / 4)) e. RR
4443, 43remulcl 5347 . . . . . 6 |- ((sin` (pi / 4)) x. (sin`
(pi / 4))) e. RR
45 0re 5452 . . . . . . 7 |- 0 e. RR
46 2pos 5991 . . . . . . 7 |- 0 < 2
4745, 1, 46ltlei 5593 . . . . . 6 |- 0 <_ 2
4843msqge0 5626 . . . . . 6 |- 0 <_ ((sin` (pi / 4)) x. (sin` (pi / 4)))
491, 44, 47, 48sqrmuli 6705 . . . . 5 |- (sqr` (2 x. ((sin` (pi / 4)) x. (sin` (pi / 4))))) = ((sqr` 2) x. (sqr` ((sin` (pi / 4)) x. (sin` (pi / 4)))))
50 sqr1 6717 . . . . 5 |- (sqr` 1) = 1
5137, 49, 503eqtr3r 1507 . . . 4 |- 1 = ((sqr`
2) x. (sqr` ((sin` (pi / 4)) x. (sin`
(pi / 4)))))
52 sqr2re 6731 . . . . . 6 |- (sqr` 2) e. RR
5352recn 5326 . . . . 5 |- (sqr` 2) e. CC
54 sqrclt 6711 . . . . . . 7 |- ((((sin`
(pi / 4)) x. (sin` (pi / 4))) e. RR /\ 0 <_ ((sin` (pi / 4)) x. (sin`
(pi / 4)))) -> (sqr`
((sin`
(pi / 4)) x. (sin` (pi / 4)))) e. RR)
5544, 48, 54mp2an 699 . . . . . 6 |- (sqr` ((sin`
(pi / 4)) x. (sin` (pi / 4)))) e. RR
5655recn 5326 . . . . 5 |- (sqr` ((sin`
(pi / 4)) x. (sin` (pi / 4)))) e. CC
57 sqr00t 6715 . . . . . . . . 9 |- ((2 e. RR /\ 0 <_ 2) -> ((sqr` 2) = 0 <-> 2 = 0))
581, 47, 57mp2an 699 . . . . . . . 8 |- ((sqr` 2) = 0 <-> 2 = 0)
5958necon3bii 1601 . . . . . . 7 |- ((sqr` 2) =/= 0 <-> 2 =/= 0)
602, 59mpbir 190 . . . . . 6 |- (sqr` 2) =/= 0
61 divmul2t 5720 . . . . . 6 |- (((1 e. CC /\ (sqr`
2) e. CC /\ (sqr`
((sin`
(pi / 4)) x. (sin` (pi / 4)))) e. CC) /\ (sqr` 2) =/= 0) -> ((1 / (sqr` 2)) = (sqr` ((sin` (pi / 4)) x. (sin` (pi / 4)))) <-> 1 = ((sqr` 2) x. (sqr` ((sin` (pi / 4)) x. (sin` (pi / 4)))))))
6260, 61mpan2 698 . . . . 5 |- ((1 e. CC /\ (sqr` 2) e. CC /\ (sqr` ((sin` (pi / 4)) x. (sin` (pi / 4)))) e. CC) -> ((1 / (sqr`
2)) = (sqr` ((sin` (pi / 4)) x. (sin` (pi / 4)))) <-> 1 = ((sqr` 2) x. (sqr` ((sin` (pi / 4)) x. (sin` (pi / 4)))))))
635, 53, 56, 62mp3an 918 . . . 4 |- ((1 / (sqr` 2)) = (sqr` ((sin` (pi / 4)) x. (sin` (pi / 4)))) <-> 1 = ((sqr` 2) x. (sqr` ((sin` (pi / 4)) x. (sin` (pi / 4))))))
6451, 63mpbir 190 . . 3 |- (1 / (sqr`
2)) = (sqr` ((sin` (pi / 4)) x. (sin` (pi / 4))))
65 pipos 8673 . . . . . . . 8 |- 0 < pi
6613, 38, 65, 39divgt0i 5862 . . . . . . 7 |- 0 < (pi / 4)
67 1re 5447 . . . . . . . 8 |- 1 e. RR
68 pigt2lt4 8670 . . . . . . . . . . 11 |- (2 < pi /\ pi < 4)
6968pm3.27i 324 . . . . . . . . . 10 |- pi < 4
7013, 38, 38, 39ltdiv1i 5825 . . . . . . . . . 10 |- (pi < 4 <-> (pi / 4) < (4 / 4))
7169, 70mpbi 189 . . . . . . . . 9 |- (pi / 4) < (4 / 4)
7238recn 5326 . . . . . . . . . 10 |- 4 e. CC
7372, 40divid 5771 . . . . . . . . 9 |- (4 / 4) = 1
7471, 73breqtr 2643 . . . . . . . 8 |- (pi / 4) < 1
7541, 67, 74ltlei 5593 . . . . . . 7 |- (pi / 4) <_ 1
76 elioc2t 6391 . . . . . . . . 9 |- ((0