El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$2 \cos{\left(\frac{x}{3} + \frac{\pi}{3} \right)} - 1 = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = 0$$
$$x_{2} = 4 \pi$$
Solución numérica$$x_{1} = 113.097335529233$$
$$x_{2} = -6.28318530717959$$
$$x_{3} = -18.8495559215388$$
$$x_{4} = -75.398223686155$$
$$x_{5} = -43.9822971502571$$
$$x_{6} = -2796.01746169492$$
$$x_{7} = 31.4159265358979$$
$$x_{8} = 15909.0251977787$$
$$x_{9} = 12.5663706143592$$
$$x_{10} = 87.9645943005142$$
$$x_{11} = -37.6991118430775$$
$$x_{12} = -100.530964914873$$
$$x_{13} = 0$$
$$x_{14} = 18.8495559215388$$
$$x_{15} = -2098.58389259798$$
$$x_{16} = -94.2477796076938$$
$$x_{17} = -81.6814089933346$$
$$x_{18} = 56.5486677646163$$
$$x_{19} = -56.5486677646163$$
$$x_{20} = 50.2654824574367$$
$$x_{21} = 94.2477796076938$$
$$x_{22} = -62.8318530717959$$
$$x_{23} = 69.1150383789755$$
$$x_{24} = 37.6991118430775$$
$$x_{25} = -25.1327412287183$$
$$x_{26} = 75.398223686155$$