The teacher will be very surprised to see your correct solution 😉
2*tan(x) - 9*cot(x) + 3 = 0
x_1 = atan(3/2)
x_2 = -atan(3)
sum
atan(3/2) + -atan(3)
=
-atan(3) + atan(3/2)
product
atan(3/2) * -atan(3)
=
-atan(3)*atan(3/2)
x1 = 82.664202716582
x2 = 49.0164366850384
x3 = -39.85791077342
x4 = 45.8748440314486
x5 = 85.8057953701718
x6 = -82.9304547657329
x7 = 23.8836954563201
x8 = -7.53223107957784
x9 = 30.1668807634997
x10 = 8.17573218837112
x11 = -64.9906520021383
x12 = -52.4242813877792
x13 = -24.149947505471
x14 = 22.9739422983759
x15 = -77.5570226164975
x16 = 80.4323632209364
x17 = 14.4589174955507
x18 = 92.9987338352955
x19 = -60.9393061906043
x20 = 5.03413953478133
x21 = 44.9650908735044
x22 = 98.3721659845309
x23 = 71.007585260167
x24 = -83.8402079236771
x25 = -29.5233796547064
x26 = -86.0720474193227
x27 = -68.1322446557281
x28 = -33.5747254662404
x29 = -5.30039158393226
x30 = -49.2826887341894
x31 = -42.9995034270098
x32 = -57.7977135370145
x33 = -71.2738373093179
x34 = 76.3810174094024
x35 = -42.0897502690656
x36 = -16.9570090403472
x37 = -79.7888621121431
x38 = 63.8146467950432
x39 = 99.2819191424751
x40 = 96.1403264888853
x41 = 74.1491779137568
x42 = 26.1155349519657
x43 = 92.0889806773513
x44 = -11.5835768911118
x45 = 4.12438637683712
x46 = -98.6384180336818
x47 = 27.0252881099099
x48 = 10.4075716840167
x49 = 89.8571411817058
x50 = 60.6730541414534
x51 = 32.3987202591453
x52 = -70.3640841513737
x53 = 54.3898688342738
x54 = -48.3729355762452
x55 = 67.8659926065772
x56 = -26.3817870011166
x57 = 77.2907705673466
x58 = 61.5828072993976
x59 = 88.9473880237615
x60 = 39.5916587242691
x61 = -93.2649858844465
x62 = -90.1233932308567
x63 = -46.1410960805996
x64 = 52.1580293386282
x65 = -76.6472694585533
x66 = 70.0978321022228
x67 = 83.5739558745262
x68 = 36.4500660706793
x69 = -74.4154299629077
x70 = -54.6561208834247
x71 = 19.8323496447861
x72 = 11.3173248419609
x73 = -86.9818005772669
x74 = -4.39063842598805
x75 = -2.15879893034246
x76 = 66.956239448633
x77 = -17.8667621982914
x78 = 38.6819055663249
x79 = 1.89254688119154
x80 = -96.4065785380363
x81 = -10.6738237331676
x82 = -64.0808988441941
x83 = -21.0083548518812
x84 = -35.806564961886
x85 = 55.299621992218
x86 = -92.3552327265023
x87 = -55.565874041369
x88 = 41.8234982199146
x89 = -32.6649723082962
x90 = -13.8154163867574
x91 = -20.098601693937
x92 = 48.1066835270942
x93 = -38.9481576154758
x94 = 58.4412146458078
x95 = -27.2915401590608
x96 = 16.6907569911963
x97 = 33.3084734170895
x98 = -61.8490593485485
x99 = -99.5481711916261
x100 = 17.6005101491405
x100 = 17.6005101491405