El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$3 \cos{\left(x \right)} - 1 = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = - \operatorname{acos}{\left(\frac{1}{3} \right)} + 2 \pi$$
$$x_{2} = \operatorname{acos}{\left(\frac{1}{3} \right)}$$
Solución numérica$$x_{1} = 45.2132565675979$$
$$x_{2} = -80.4504495759938$$
$$x_{3} = -82.9123684106754$$
$$x_{4} = 5.05222588983881$$
$$x_{5} = -93.016820190353$$
$$x_{6} = 20.0805153388795$$
$$x_{7} = 95.4787390250346$$
$$x_{8} = -74.1672642688143$$
$$x_{9} = 61.6008936544551$$
$$x_{10} = -11.3354111970184$$
$$x_{11} = -95.4787390250346$$
$$x_{12} = -49.0345230400959$$
$$x_{13} = -26.3637006460591$$
$$x_{14} = 38.9300712604183$$
$$x_{15} = 36.4681524257367$$
$$x_{16} = 7.51414472452036$$
$$x_{17} = -17.618596504198$$
$$x_{18} = 82.9123684106754$$
$$x_{19} = 99.3000054975326$$
$$x_{20} = -70.3459977963162$$
$$x_{21} = 86.7336348831734$$
$$x_{22} = -61.6008936544551$$
$$x_{23} = 51.4964418747775$$
$$x_{24} = -7.51414472452036$$
$$x_{25} = -45.2132565675979$$
$$x_{26} = -55.3177083472755$$
$$x_{27} = 32.6468859532387$$
$$x_{28} = 42.7513377329163$$
$$x_{29} = 89.195553717855$$
$$x_{30} = 26.3637006460591$$
$$x_{31} = -23.9017818113776$$
$$x_{32} = 30.1849671185572$$
$$x_{33} = 13.7973300316999$$
$$x_{34} = -57.7796271819571$$
$$x_{35} = -86.7336348831734$$
$$x_{36} = 23.9017818113776$$
$$x_{37} = -76.6291831034958$$
$$x_{38} = -42.7513377329163$$
$$x_{39} = 67.8840789616347$$
$$x_{40} = 17.618596504198$$
$$x_{41} = -13.7973300316999$$
$$x_{42} = -1.23095941734077$$
$$x_{43} = 76.6291831034958$$
$$x_{44} = 1.23095941734077$$
$$x_{45} = -20.0805153388795$$
$$x_{46} = -99.3000054975326$$
$$x_{47} = 49.0345230400959$$
$$x_{48} = 64.0628124891366$$
$$x_{49} = -64.0628124891366$$
$$x_{50} = 55.3177083472755$$
$$x_{51} = 74.1672642688143$$
$$x_{52} = -30.1849671185572$$
$$x_{53} = -38.9300712604183$$
$$x_{54} = -51.4964418747775$$
$$x_{55} = -5.05222588983881$$
$$x_{56} = -325.494676555998$$
$$x_{57} = -67.8840789616347$$
$$x_{58} = 57.7796271819571$$
$$x_{59} = -89.195553717855$$
$$x_{60} = 11.3354111970184$$
$$x_{61} = -32.6468859532387$$
$$x_{62} = 80.4504495759938$$
$$x_{63} = 93.016820190353$$
$$x_{64} = -36.4681524257367$$
$$x_{65} = -101.761924332214$$
$$x_{66} = 70.3459977963162$$