El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\left(-3\right) \cos^{2}{\left(x + \frac{\pi}{3} \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = \frac{\pi}{6}$$
$$x_{2} = \frac{7 \pi}{6}$$
Solución numérica$$x_{1} = 0.523598630383231$$
$$x_{2} = 22.5147472092341$$
$$x_{3} = 47.6474887742656$$
$$x_{4} = 9.94837678454496$$
$$x_{5} = 50.7890810020498$$
$$x_{6} = -49.7418836877494$$
$$x_{7} = 60.2138592238034$$
$$x_{8} = 6.80678384818368$$
$$x_{9} = 31.9395253661994$$
$$x_{10} = 79.0634148782955$$
$$x_{11} = 69.6386373523876$$
$$x_{12} = -15.1843647286274$$
$$x_{13} = 44.5058957881351$$
$$x_{14} = -81.1578104585483$$
$$x_{15} = 97.912971109499$$
$$x_{16} = 63.3554520899367$$
$$x_{17} = -40.3171055388413$$
$$x_{18} = -2.61799362374048$$
$$x_{19} = -59.1666618819956$$
$$x_{20} = 85.3466006207689$$
$$x_{21} = 3.66519161783543$$
$$x_{22} = -24.609141994629$$
$$x_{23} = -74.8746246952228$$
$$x_{24} = 72.780229579101$$
$$x_{25} = -93.7241808501923$$
$$x_{26} = -62.3082541172719$$
$$x_{27} = -96.8657736946942$$
$$x_{28} = 41.3643035631668$$
$$x_{29} = 25.6563403116681$$
$$x_{30} = -8.90117941081158$$
$$x_{31} = -96.86577326587$$
$$x_{32} = -30.8923279823281$$
$$x_{33} = 101.054563451242$$
$$x_{34} = 79.0634152866065$$
$$x_{35} = 57.0722667194141$$
$$x_{36} = 38.2227106406249$$
$$x_{37} = -52.8834765534979$$
$$x_{38} = -56.0250689628598$$
$$x_{39} = -90.5825875607171$$
$$x_{40} = -8.90117898570915$$
$$x_{41} = 25.6563401960814$$
$$x_{42} = 19.3731549520965$$
$$x_{43} = -2.61799347849336$$
$$x_{44} = 6.8067838005344$$
$$x_{45} = 28.7979324250767$$
$$x_{46} = -78.0162175464461$$
$$x_{47} = 57.0722663056004$$
$$x_{48} = 13.0899695832072$$
$$x_{49} = 19.3731550404632$$
$$x_{50} = -100.007366130823$$
$$x_{51} = 41.3643035278316$$
$$x_{52} = 66.4970443670865$$
$$x_{53} = -24.6091421996767$$
$$x_{54} = 13.0899691610288$$
$$x_{55} = -34.033920379906$$
$$x_{56} = 35.0811177331724$$
$$x_{57} = -43.4586985271673$$
$$x_{58} = -27.7507351061628$$
$$x_{59} = 82.2050078076174$$
$$x_{60} = -68.5914393518369$$
$$x_{61} = -59.1666622564215$$
$$x_{62} = -52.8834761249596$$
$$x_{63} = -74.8746251242959$$
$$x_{64} = -87.4409956845148$$
$$x_{65} = -81.1578107857198$$
$$x_{66} = -84.2994026957641$$
$$x_{67} = -18.3259569604722$$
$$x_{68} = -5.75958652427741$$
$$x_{69} = 53.9306739475496$$
$$x_{70} = -71.7330322690809$$
$$x_{71} = 16.2315620579617$$
$$x_{72} = 85.3466006789848$$
$$x_{73} = 679.107612027751$$
$$x_{74} = -12.0427717974673$$
$$x_{75} = 63.355452103462$$
$$x_{76} = -46.6002905100193$$
$$x_{77} = -21.4675499484173$$
$$x_{78} = -90.5825879280564$$
$$x_{79} = 35.0811181515971$$
$$x_{80} = 88.4881929460882$$
$$x_{81} = -37.1755133053546$$
$$x_{82} = -68.591439029003$$
$$x_{83} = 94.7713781562287$$
$$x_{84} = -65.4498471058665$$
$$x_{85} = 75.9218225286381$$
$$x_{86} = -46.6002907757096$$
$$x_{87} = -30.8923275551105$$
$$x_{88} = 91.6297859304472$$
$$x_{89} = -37.1755136996328$$
$$x_{90} = -15.1843650731387$$