The teacher will be very surprised to see your correct solution 😉
___ cos(x) = \/ 2 *sin(x)
Divide both parts of the equation by -sqrt(2)
sum
/ ___\ |\/ 2 | atan|-----| \ 2 /
=
/ ___\ |\/ 2 | atan|-----| \ 2 /
product
/ ___\ |\/ 2 | atan|-----| \ 2 /
=
/ ___\ |\/ 2 | atan|-----| \ 2 /
atan(sqrt(2)/2)
/ ___\ |\/ 2 | x1 = atan|-----| \ 2 /
x1 = atan(sqrt(2)/2)
x1 = 19.4650356302091
x2 = 22.6066282837989
x3 = -2.52611294491941
x4 = 35.1729988981581
x5 = 50.8809621661071
x6 = -84.207521938254
x7 = -77.9243366310744
x8 = -90.4907072454336
x9 = -74.7827439774847
x10 = 72.8721107412356
x11 = 76.0137033948254
x12 = -33.9420394808173
x13 = 82.296888702005
x14 = 69.7305180876458
x15 = -87.3491145918438
x16 = 3.75707236226018
x17 = 38.3145915517479
x18 = -55.9331880559459
x19 = 63.4473327804663
x20 = -5.6677055985092
x21 = -24.517261520048
x22 = 47.7393695125173
x23 = 255.084484649444
x24 = 66.5889254340561
x25 = 10.0402576694398
x26 = -27.6588541736378
x27 = 32.0314062445683
x28 = -8.80929825209899
x29 = -46.5084100951765
x30 = 13.1818503230296
x31 = 25.7482209373887
x32 = 94.8632593163642
x33 = 91.7216666627744
x34 = -62.2163733631255
x35 = 85.4384813555948
x36 = -96.7738925526132
x37 = -15.0924835592786
x38 = -18.2340762128684
x39 = -40.2252247879969
x40 = 41.4561842053377
x41 = 44.5977768589275
x42 = 28.8898135909785
x43 = 79.1552960484152
x44 = -68.4995586703051
x45 = -65.3579660167153
x46 = -43.3668174415867
x47 = -49.6500027487663
x48 = -81.0659292846642
x49 = 16.3234429766194
x50 = 60.3057401268765
x51 = -37.0836321344071
x52 = 54.0225548196969
x53 = 98.004851969954
x54 = 6.89866501584997
x55 = 88.5800740091846
x56 = -30.8004468272275
x57 = -99.915485206203
x58 = -52.7915954023561
x59 = -11.9508909056888
x60 = -21.3756688664582
x61 = -59.0747807095357
x62 = 101.146444623544
x63 = -71.6411513238949
x64 = 57.1641474732867
x65 = -93.6322998990234
x66 = 0.615479708670387
x66 = 0.615479708670387