cos(3*x)=cos(15*x)

$$cos{left (3 x right )} = cos{left (15 x right )}$$

$$x_{1} = 0$$

x2 = pi

$$x_{2} = pi$$

/ 9 ____
x3 = -I*log -/ -1 /

$$x_{3} = – i log{left (- sqrt[9]{-1} right )}$$

/ 2/9
x4 = -I*log -(-1) /

$$x_{4} = – i log{left (- left(-1right)^{frac{2}{9}} right )}$$

/ 7/9
x5 = -I*log(-1) /

$$x_{5} = – i log{left (left(-1right)^{frac{7}{9}} right )}$$

/ 8/9
x6 = -I*log(-1) /

$$x_{6} = – i log{left (left(-1right)^{frac{8}{9}} right )}$$

/ ___
| 1 I*/ 3 |
x7 = -I*log|- – – ——-|
2 2 /

$$x_{7} = – i log{left (- frac{1}{2} – frac{sqrt{3} i}{2} right )}$$

/ ___
| 1 I*/ 3 |
x8 = -I*log|- – + ——-|
2 2 /

$$x_{8} = – i log{left (- frac{1}{2} + frac{sqrt{3} i}{2} right )}$$

/ ___
|1 I*/ 3 |
x9 = -I*log|- – ——-|
2 2 /

$$x_{9} = – i log{left (frac{1}{2} – frac{sqrt{3} i}{2} right )}$$

/ ___
|1 I*/ 3 |
x10 = -I*log|- + ——-|
2 2 /

$$x_{10} = – i log{left (frac{1}{2} + frac{sqrt{3} i}{2} right )}$$

/ /pi
/ _____________________ |cos|–||
| / 2/pi 2/pi | | 18/|
x11 = -pi – I*log| / cos |–| + sin |–| | + atan|——-|
/ 18/ 18/ / | /pi|
|sin|–||
18//

$$x_{11} = – pi + {atan}{left (frac{cos{left (frac{pi}{18} right )}}{sin{left (frac{pi}{18} right )}} right )} – i log{left (sqrt{sin^{2}{left (frac{pi}{18} right )} + cos^{2}{left (frac{pi}{18} right )}} right )}$$

/ /pi
|cos|–|| / _____________________
| 18/| | / 2/pi 2/pi |
x12 = pi – atan|——-| – I*log| / cos |–| + sin |–| |
| /pi| / 18/ 18/ /
|sin|–||
18//

$$x_{12} = – {atan}{left (frac{cos{left (frac{pi}{18} right )}}{sin{left (frac{pi}{18} right )}} right )} + pi – i log{left (sqrt{sin^{2}{left (frac{pi}{18} right )} + cos^{2}{left (frac{pi}{18} right )}} right )}$$

/ /pi
|cos|–|| / _____________________
| 18/| | / 2/pi 2/pi |
x13 = – atan|——-| – I*log| / cos |–| + sin |–| |
| /pi| / 18/ 18/ /
|sin|–||
18//

$$x_{13} = – {atan}{left (frac{cos{left (frac{pi}{18} right )}}{sin{left (frac{pi}{18} right )}} right )} – i log{left (sqrt{sin^{2}{left (frac{pi}{18} right )} + cos^{2}{left (frac{pi}{18} right )}} right )}$$

/ /pi
/ _____________________ |cos|–||
| / 2/pi 2/pi | | 18/|
x14 = – I*log| / cos |–| + sin |–| | + atan|——-|
/ 18/ 18/ / | /pi|
|sin|–||
18//

$$x_{14} = {atan}{left (frac{cos{left (frac{pi}{18} right )}}{sin{left (frac{pi}{18} right )}} right )} – i log{left (sqrt{sin^{2}{left (frac{pi}{18} right )} + cos^{2}{left (frac{pi}{18} right )}} right )}$$

/ -2*pi*I
| ——-|
| 9 |
x15 = -I*loge /

$$x_{15} = – i log{left (e^{- frac{2 pi}{9} i} right )}$$

/ -pi*I
| ——|
| 9 |
x16 = -I*loge /

$$x_{16} = – i log{left (e^{- frac{i pi}{9}} right )}$$

/ pi*I
| —-|
| 9 |
x17 = -I*loge /

$$x_{17} = – i log{left (e^{frac{i pi}{9}} right )}$$

/ 2*pi*I
| ——|
| 9 |
x18 = -I*loge /

$$x_{18} = – i log{left (e^{frac{2 pi}{9} i} right )}$$

x1 = -100.007366139000

x2 = 21.9911485832000

x3 = -503.003890425000

x4 = -23.7364778271000

x5 = 95.9931088597000

x6 = -1.74532925199000

x7 = -51.8362787842000

x8 = -75.7472895366000

x9 = -39.7935069061000

x10 = -74.0019602846000

x11 = 36.1283155163000

x12 = -71.7330322570000

x13 = 48.1710873782000

x14 = 23.5619449019000

x15 = 14.1371669412000

x16 = 28.2743338721000

x17 = 32.1140582367000

x18 = -5.75958653158000

x19 = -15.7079632410000

x20 = -7.85398163397000

x21 = -53.7561409614000

x22 = -42.2369678983000

x23 = 38.2227106187000

x24 = 89.3608577021000

x25 = -17.8023583241000

x26 = -95.6440430093000

x27 = 26.1799388284000

x28 = -27.7507351067000

x29 = -65.9734457811000

x30 = 87.9645943009000

x31 = 38.3972435439000

x32 = -79.9360797413000

x33 = -31.7649923863000

x34 = 65.9734457354000

x35 = -43.9822971825000

x36 = 92.5024503557000

x37 = 43.9822971616000

x38 = -11.8682389136000

x39 = -70.1622359874000

x40 = -25.8308729295000

x41 = -3.83972435439000

x42 = -33.1612557879000

x43 = 84.4739357965000

x44 = 6.28318530287000

x45 = 0.0

x46 = 16.2315620435000

x47 = -57.9449311662000

x48 = -13.9626340160000

x49 = 86.3937979737000

x50 = -87.9645943788000

x51 = -49.7418836818000

x52 = 78.8888821901000

x53 = -93.7241808321000

x54 = 52.0108117094000

x55 = -35.9537825911000

x56 = 74.0019602846000

x57 = 34.2084533391000

x58 = -83.7758040730000

x59 = -61.7846554894000

x60 = 55.8505360638000

x61 = -45.5530934771000

x62 = 54.1052068118000

x63 = 50.2654824485000

x64 = 86.2192650485000

x65 = 76.0963553870000

x66 = 20.2458193231000

x67 = 10.1229096616000

x68 = 60.3883921190000

x69 = -47.8220215046000

x70 = -91.8043186549000

x71 = -88.6627260013000

x72 = -29.8451302091000

x73 = -33.8593874887000

x74 = -78.0162175641000

x75 = 94.2477796094000

x76 = 1.74532925199000

x77 = 63.8790505605000

x78 = 18.1514242207000

x79 = -8.90117918517000

x80 = 58.1194640914000

x81 = -97.7384381117000

x82 = -69.8131700798000

x83 = 98.0875039621000

x84 = 4.18879025535000

x85 = 42.2369678983000

x86 = 64.2281164734000

x87 = 10.4719754616000

x88 = -65.2753140246000

x89 = 72.2566310280000

x90 = -20.4203522483000

x91 = 8.02851455917000

x92 = 70.6858347058000

x93 = -21.9911485885000