El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\sin{\left(3 x \right)} - 2 \cos{\left(3 x \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = \frac{\operatorname{atan}{\left(2 \right)}}{3}$$
Solución numérica$$x_{1} = -87.5955447279162$$
$$x_{2} = -1.72534552979517$$
$$x_{3} = 9.79382753336741$$
$$x_{4} = -69.793186357574$$
$$x_{5} = 99.8528169362748$$
$$x_{6} = 31.784976108496$$
$$x_{7} = -98.0675202398822$$
$$x_{8} = 84.1448536683259$$
$$x_{9} = -32.0940745144965$$
$$x_{10} = 11.8882226357606$$
$$x_{11} = 97.7584218338816$$
$$x_{12} = -76.0763716647536$$
$$x_{13} = -85.501149625523$$
$$x_{14} = -51.9908279872319$$
$$x_{15} = 40.1625565180687$$
$$x_{16} = -36.2828647192829$$
$$x_{17} = 56.9177173372143$$
$$x_{18} = 35.9737663132824$$
$$x_{19} = -27.9052843097101$$
$$x_{20} = -25.8108892073169$$
$$x_{21} = 66.3424952979837$$
$$x_{22} = -12.1973210417611$$
$$x_{23} = 2983.8348729317$$
$$x_{24} = -14.2917161441543$$
$$x_{25} = 57.9649148884109$$
$$x_{26} = 86.239248770719$$
$$x_{27} = 26.548988352513$$
$$x_{28} = -65.6043961527876$$
$$x_{29} = -54.0852230896251$$
$$x_{30} = 46.4457418252483$$
$$x_{31} = 33.8793712108892$$
$$x_{32} = 48.5401369276415$$
$$x_{33} = 82.0504585659327$$
$$x_{34} = -3497.27077142404$$
$$x_{35} = 2.46344467499123$$
$$x_{36} = 53.7761246836245$$
$$x_{37} = 44.3513467228551$$
$$x_{38} = -62.4628034991978$$
$$x_{39} = 20.2658030453334$$
$$x_{40} = -5.91413573458156$$
$$x_{41} = 18.1714079429402$$
$$x_{42} = -59.321210845608$$
$$x_{43} = -43.6132475776591$$
$$x_{44} = -95.973125137489$$
$$x_{45} = 29.6905810061028$$
$$x_{46} = 50.6345320300347$$
$$x_{47} = 38.0681614156755$$
$$x_{48} = -93.8787300350958$$
$$x_{49} = -67.6987912551808$$
$$x_{50} = 92.5224340778986$$
$$x_{51} = 16.077012840547$$
$$x_{52} = 72.6256806051633$$
$$x_{53} = -34.1884696168897$$
$$x_{54} = -47.8020377824455$$
$$x_{55} = 88.3336438731122$$
$$x_{56} = -23.7164941049237$$
$$x_{57} = 64.2481001955905$$
$$x_{58} = 0.36904957259803$$
$$x_{59} = -100.161915342275$$
$$x_{60} = -41.5188524752659$$
$$x_{61} = 55.8705197860177$$
$$x_{62} = -63.5100010503944$$
$$x_{63} = -73.9819765623604$$
$$x_{64} = 13.9826177381538$$
$$x_{65} = 77.8616683611463$$
$$x_{66} = 96.711224282685$$
$$x_{67} = 70.5312855027701$$
$$x_{68} = -8.00853083697475$$
$$x_{69} = 60.0593099908041$$
$$x_{70} = 7.69943243097421$$
$$x_{71} = -71.8875814599672$$
$$x_{72} = -80.26516186954$$
$$x_{73} = -56.1796181920182$$
$$x_{74} = -10.1029259393679$$
$$x_{75} = 90.4280389755054$$
$$x_{76} = 24.4545932501198$$
$$x_{77} = -58.2740132944114$$
$$x_{78} = -45.7076426800523$$
$$x_{79} = -120.058668815011$$
$$x_{80} = -49.8964328848387$$
$$x_{81} = -84.4539520743264$$
$$x_{82} = 22.3601981477266$$
$$x_{83} = -21.6220990025305$$
$$x_{84} = 62.1537050931973$$
$$x_{85} = 4.55783977738442$$
$$x_{86} = -905.456832212459$$
$$x_{87} = 75.7672732587531$$
$$x_{88} = 93.5696316290952$$
$$x_{89} = 42.2569516204619$$
$$x_{90} = -89.6899398303094$$
$$x_{91} = -91.7843349327026$$
$$x_{92} = 79.9560634635395$$
$$x_{93} = -19.5277039001373$$
$$x_{94} = -29.9996794121033$$
$$x_{95} = 68.4368904003769$$
$$x_{96} = -3.81974063218836$$
$$x_{97} = -78.1707667671468$$
$$x_{98} = -38.3772598216761$$