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$$x_{1} = -23.2221079924693$$
$$x_{2} = -45.8929303865061$$
$$x_{3} = 73.487590449906$$
$$x_{4} = 27.0433744649674$$
$$x_{5} = 98.6203316786244$$
$$x_{6} = 14.4770038506082$$
$$x_{7} = 20.7601891577878$$
$$x_{8} = 60.9212198355468$$
$$x_{9} = -96.1584128439428$$
$$x_{10} = -60.9212198355468$$
$$x_{11} = 33.326559772147$$
$$x_{12} = 3426.24662564912$$
$$x_{13} = 35.7884786068285$$
$$x_{14} = 29.5052932996489$$
$$x_{15} = -16.9389226852897$$
$$x_{16} = -54.6380345283673$$
$$x_{17} = 16.9389226852897$$
$$x_{18} = 83.5920422295836$$
$$x_{19} = 64.7424863080449$$
$$x_{20} = -10.6557373781102$$
$$x_{21} = -7726.40729459464$$
$$x_{22} = 89.8752275367632$$
$$x_{23} = 155.168999443241$$
$$x_{24} = 10.6557373781102$$
$$x_{25} = -48.3548492211877$$
$$x_{26} = -86.0539610642652$$
$$x_{27} = 71.0256716152245$$
$$x_{28} = 45.8929303865061$$
$$x_{29} = 79.7707757570856$$
$$x_{30} = 23.2221079924693$$
$$x_{31} = 39.6097450793265$$
$$x_{32} = 86.0539610642652$$
$$x_{33} = -1.91063323624902$$
$$x_{34} = -42.0716639140081$$
$$x_{35} = -20.7601891577878$$
$$x_{36} = 67.2044051427264$$
$$x_{37} = -77.3088569224041$$
$$x_{38} = 52.1761156936857$$
$$x_{39} = -79.7707757570856$$
$$x_{40} = -14.4770038506082$$
$$x_{41} = 42.0716639140081$$
$$x_{42} = -73.487590449906$$
$$x_{43} = -33.326559772147$$
$$x_{44} = -39.6097450793265$$
$$x_{45} = -35.7884786068285$$
$$x_{46} = 96.1584128439428$$
$$x_{47} = -52.1761156936857$$
$$x_{48} = -67.2044051427264$$
$$x_{49} = -71.0256716152245$$
$$x_{50} = 1.91063323624902$$
$$x_{51} = 92.3371463714448$$
$$x_{52} = -58.4593010008653$$
$$x_{53} = -27.0433744649674$$
$$x_{54} = 8.19381854342861$$
$$x_{55} = 77.3088569224041$$
$$x_{56} = -4.37255207093057$$
$$x_{57} = -64.7424863080449$$
$$x_{58} = -8.19381854342861$$
$$x_{59} = -89.8752275367632$$
$$x_{60} = -29.5052932996489$$
$$x_{61} = 58.4593010008653$$
$$x_{62} = -971.983089376587$$
$$x_{63} = 4.37255207093057$$
$$x_{64} = -98.6203316786244$$
$$x_{65} = -92.3371463714448$$
$$x_{66} = 48.3548492211877$$
$$x_{67} = 54.6380345283673$$
$$x_{68} = -83.5920422295836$$