The teacher will be very surprised to see your correct solution 😉
/pi \ cos|-- - 4*x| = 1 \9 /
sum
pi -- 36
=
pi -- 36
product
pi -- 36
=
pi -- 36
pi/36
x1 = -12.4791042131093
x2 = 37.7863784216865
x3 = 78.6270826988203
x4 = 0.0872667782384371
x5 = -53.3198087067381
x6 = 42.4987671739903
x7 = 15.7952298446077
x8 = 34.6447855586004
x9 = 81.7686755752369
x10 = 72.3438974380663
x11 = -80.0233461796468
x12 = 95.9058424699032
x13 = -72.1693648950812
x14 = 45.6403600519256
x15 = -28.1870673101421
x16 = 92.7642500048763
x17 = 14.2244334242509
x18 = -86.3065313879892
x19 = -7.76671515834831
x20 = 56.6359341282408
x21 = 67.6315086235637
x22 = 28.361600279185
x23 = 86.4810643279505
x24 = 80.197879175411
x25 = 6.37045169996086
x26 = -72.1693644656717
x27 = 51.9235453097555
x28 = 29.9323967292291
x29 = 73.9146938899713
x30 = -20.3330856661766
x31 = -34.4702527562253
x32 = 75.4854898875476
x33 = -14.049900432901
x34 = -59.602994036852
x35 = 97.4766384139647
x36 = -56.4614013050312
x37 = -15.6206968791201
x38 = 12.6536369900585
x39 = 94.3350460177276
x40 = -94.1605130437285
x41 = -95.7313094851324
x42 = 53.4943413718914
x43 = -75.3109572683443
x44 = -9.33751157718683
x45 = 88.0518606536713
x46 = 44.0695634005613
x47 = 50.3527488585529
x48 = -97.3021058272143
x49 = -100.443698415653
x50 = 58.2067305910165
x51 = -81.5941426155007
x52 = 64.4899157508705
x53 = -37.611845458058
x54 = 22.0784149665373
x55 = -45.465827131301
x56 = 48.7819528362493
x57 = 70.7731014780795
x58 = -1.48352997912758
x59 = -42.3242342397544
x60 = -12.4791042029249
x61 = 100.618231270209
x62 = -78.452549858469
x63 = -6.19591873266924
x64 = 7.94124814835801
x65 = -29.7578637405335
x66 = 66.0607120362936
x67 = 23.6492114797134
x68 = 36.2155820073397
x69 = -58.0321975968207
x70 = 20.5076185973203
x71 = -67.4569757069933
x72 = -43.8950303690659
x73 = -51.7490123223636
x74 = 1.65806290699436
x75 = 9.5120443231479
x76 = -89.4481242823959
x77 = -50.1782158878097
x78 = -31.3286601428889
x79 = -50.1782159947367
x80 = -64.3153828137022
x81 = 89.6226571945447
x82 = -23.4746785553399
x83 = -36.0410490146034
x84 = -73.7401609038844
x85 = 31.5031928515163
x86 = 59.7775269985642
x86 = 59.7775269985642