El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$- \frac{2 \cos{\left(\frac{x}{4} + \frac{\pi}{5} \right)}}{5} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = \frac{6 \pi}{5}$$
$$x_{2} = \frac{26 \pi}{5}$$
Solución numérica$$x_{1} = 16.3362817986669$$
$$x_{2} = -1215.16803840853$$
$$x_{3} = -71.6283125018473$$
$$x_{4} = 343.061917772005$$
$$x_{5} = -59.0619418874881$$
$$x_{6} = 3.76991118430775$$
$$x_{7} = -33.9292006587698$$
$$x_{8} = -84.1946831162065$$
$$x_{9} = 619.522071287907$$
$$x_{10} = -21.3628300444106$$
$$x_{11} = 179.699099785336$$
$$x_{12} = -59962.9506605377$$
$$x_{13} = 91.734505484822$$
$$x_{14} = 54.0353936417444$$
$$x_{15} = 104.300876099181$$
$$x_{16} = -96.7610537305656$$
$$x_{17} = 242.530952857132$$
$$x_{18} = 79.1681348704628$$
$$x_{19} = -46.4955712731289$$
$$x_{20} = -109.327424344925$$
$$x_{21} = 66.6017642561036$$
$$x_{22} = 41.4690230273853$$
$$x_{23} = 28.9026524130261$$
$$x_{24} = -8.79645943005142$$
$$x_{25} = 6249.25610652082$$