El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\cos{\left(\frac{x}{4} \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = 2 \pi$$
$$x_{2} = 6 \pi$$
Solución numérica$$x_{1} = 31.4159265358979$$
$$x_{2} = -56.5486677646163$$
$$x_{3} = 69.1150383789755$$
$$x_{4} = -81.6814089933346$$
$$x_{5} = 1602.21225333079$$
$$x_{6} = -953517.352661652$$
$$x_{7} = 106.814150222053$$
$$x_{8} = 6465.39768108779$$
$$x_{9} = -94.2477796076938$$
$$x_{10} = 6.28318530717959$$
$$x_{11} = -69.1150383789755$$
$$x_{12} = -18.8495559215388$$
$$x_{13} = 18.8495559215388$$
$$x_{14} = -43.9822971502571$$
$$x_{15} = -6.28318530717959$$
$$x_{16} = 43.9822971502571$$
$$x_{17} = 56.5486677646163$$
$$x_{18} = 5447.5216613247$$
$$x_{19} = 81.6814089933346$$
$$x_{20} = -31.4159265358979$$
$$x_{21} = 94.2477796076938$$
$$x_{22} = -7420.44184777909$$