The teacher will be very surprised to see your correct solution 😉
___ -\/ 3 cos(-2*x) = ------- 2
5*pi x1 = ---- 12
7*pi x2 = ---- 12
x2 = 7*pi/12
sum
5*pi 7*pi ---- + ---- 12 12
=
pi
product
5*pi 7*pi ----*---- 12 12
=
2 35*pi ------ 144
35*pi^2/144
x1 = -13.8753675533549
x2 = 39.5317075576716
x3 = -58.3812634792103
x4 = 1336.48587471466
x5 = 1.83259571459405
x6 = -26.9653369433124
x7 = 80.3724120543389
x8 = -1899.35455848283
x9 = 10.7337748997651
x10 = 82.9904059323304
x11 = 60.9992573572018
x12 = 33.248522250492
x13 = -4.97418836818384
x14 = -55.2396708256205
x15 = 11.2573736753634
x16 = -82.9904059323304
x17 = -30.1069295969022
x18 = -74.0892267471593
x19 = -45.8148928648512
x20 = -48.4328867428426
x21 = 42.1497014356631
x22 = 17.540558982543
x23 = 61.5228561328001
x24 = 77.2308194007491
x25 = -48.9564855184409
x26 = -35.8665161284835
x27 = -70.4240353179712
x28 = -17.540558982543
x29 = -61.5228561328001
x30 = -99.2219679758776
x31 = -79.8488132787406
x32 = 89.7971900151083
x33 = 48.4328867428426
x34 = -89.7971900151083
x35 = 35.8665161284835
x36 = -98.6983692002793
x37 = -96.0803753222878
x38 = -52.0980781720307
x39 = 58.3812634792103
x40 = -20.1585528605345
x41 = -32.7249234748937
x42 = 54.7160720500222
x43 = 17.0169602069447
x44 = 20.1585528605345
x45 = 70.4240353179712
x46 = 67.8060414399797
x47 = -39.5317075576716
x48 = 98.6983692002793
x49 = -228.027266773059
x50 = 83.5140047079287
x51 = -77.2308194007491
x52 = 92.4151838930998
x53 = -11.2573736753634
x54 = 64.1408500107916
x55 = 45.8148928648512
x56 = -67.8060414399797
x57 = 99.2219679758776
x58 = 4.45058959258554
x59 = 96.0803753222878
x60 = -1.30899693899575
x61 = -8.11578102177363
x62 = 86.1319985859202
x63 = 76.7072206251508
x64 = 26.4417381677141
x65 = 23.8237442897226
x66 = 32.7249234748937
x67 = -10.7337748997651
x68 = -92.9387826686981
x69 = -86.1319985859202
x70 = -1.83259571459405
x71 = -33.248522250492
x72 = 30.1069295969022
x73 = -83.5140047079287
x74 = 3925.15822127265
x75 = 52.0980781720307
x76 = -26.4417381677141
x77 = -70.9476340935695
x78 = 55.2396708256205
x79 = 74.0892267471593
x80 = -42.1497014356631
x81 = 8.11578102177363
x82 = -89.27359123951
x83 = -64.1408500107916
x84 = -23.8237442897226
x85 = 13.8753675533549
x86 = -45.2912940892529
x87 = -76.7072206251508
x88 = -54.7160720500222
x89 = -57.857664703612
x90 = -92.4151838930998
x91 = 39.0081087820733
x92 = -4.45058959258554
x92 = -4.45058959258554