El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\left(\left(- \cos{\left(x \right)} - \cos{\left(2 x \right)}\right) - \sin{\left(x \right)}\right) - \sin{\left(2 x \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = - \pi$$
$$x_{2} = - \frac{5 \pi}{6}$$
$$x_{3} = - \frac{\pi}{6}$$
$$x_{4} = \frac{\pi}{2}$$
$$x_{5} = \pi$$
Solución numérica$$x_{1} = -59.6902604182061$$
$$x_{2} = 7.85398163397448$$
$$x_{3} = -69.6386371545737$$
$$x_{4} = -25.6563400043166$$
$$x_{5} = 41.3643032722656$$
$$x_{6} = -2.61799387799149$$
$$x_{7} = -21.9911485751286$$
$$x_{8} = -31.9395253114962$$
$$x_{9} = -34.0339204138894$$
$$x_{10} = -46.6002910282486$$
$$x_{11} = -84.2994028713261$$
$$x_{12} = -88.4881930761125$$
$$x_{13} = 95.8185759344887$$
$$x_{14} = 34.5575191894877$$
$$x_{15} = -86.3937979737193$$
$$x_{16} = -10.9955742875643$$
$$x_{17} = -0.523598775598299$$
$$x_{18} = 26.7035375555132$$
$$x_{19} = -40.317105721069$$
$$x_{20} = 32.9867228626928$$
$$x_{21} = 97.9129710368819$$
$$x_{22} = 60.2138591938044$$
$$x_{23} = -80.1106126665397$$
$$x_{24} = -65.9734457253857$$
$$x_{25} = 53.9306738866248$$
$$x_{26} = 51.8362787842316$$
$$x_{27} = 76.9690200129499$$
$$x_{28} = 16.2315620435473$$
$$x_{29} = 91.6297857297023$$
$$x_{30} = 20.4203522483337$$
$$x_{31} = -82.2050077689329$$
$$x_{32} = -73.8274273593601$$
$$x_{33} = 47.6474885794452$$
$$x_{34} = 87.4409955249159$$
$$x_{35} = 62.3082542961976$$
$$x_{36} = 72.2566310325652$$
$$x_{37} = -52.8834763354282$$
$$x_{38} = -90.5825881785057$$
$$x_{39} = -9.42477796076938$$
$$x_{40} = -29.845130209103$$
$$x_{41} = 64.4026493985908$$
$$x_{42} = -63.3554518473942$$
$$x_{43} = 18.3259571459405$$
$$x_{44} = 43.4586983746588$$
$$x_{45} = 28.2743338823081$$
$$x_{46} = 24.60914245312$$
$$x_{47} = -67.5442420521806$$
$$x_{48} = -53.4070751110265$$
$$x_{49} = 21.9911485751286$$
$$x_{50} = -36.1283155162826$$
$$x_{51} = -15.707963267949$$
$$x_{52} = -75.9218224617533$$
$$x_{53} = -19.3731546971371$$
$$x_{54} = 65.9734457253857$$
$$x_{55} = -44.5058959258554$$
$$x_{56} = 14.1371669411541$$
$$x_{57} = 85.3466004225227$$
$$x_{58} = 78.5398163397448$$
$$x_{59} = -27.7507351067098$$
$$x_{60} = -38.2227106186758$$
$$x_{61} = 68.5914396033772$$
$$x_{62} = -97.3893722612836$$
$$x_{63} = 100.007366139275$$
$$x_{64} = 67478.2686064552$$
$$x_{65} = 70.6858347057703$$
$$x_{66} = 30.8923277602996$$
$$x_{67} = -78.0162175641465$$
$$x_{68} = 12.0427718387609$$
$$x_{69} = -23.5619449019235$$
$$x_{70} = 5.75958653158129$$
$$x_{71} = -71.733032256967$$
$$x_{72} = 35.081117965086$$
$$x_{73} = 3.66519142918809$$
$$x_{74} = 9.94837673636768$$
$$x_{75} = -17.2787595947439$$
$$x_{76} = 93.7241808320955$$
$$x_{77} = 1.5707963267949$$
$$x_{78} = 58.1194640914112$$
$$x_{79} = -61.261056745001$$
$$x_{80} = 49.7418836818384$$
$$x_{81} = 56.025068989018$$
$$x_{82} = -42.4115008234622$$