El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$4 \cos{\left(x \right)} - 3 = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = - \operatorname{acos}{\left(\frac{3}{4} \right)} + 2 \pi$$
$$x_{2} = \operatorname{acos}{\left(\frac{3}{4} \right)}$$
Solución numérica$$x_{1} = 13.2891048621726$$
$$x_{2} = -18.1268216737253$$
$$x_{3} = 43.2595629024437$$
$$x_{4} = 74.6754894383416$$
$$x_{5} = -13.2891048621726$$
$$x_{6} = -43.2595629024437$$
$$x_{7} = -94.9705138555072$$
$$x_{8} = 87.2418600527008$$
$$x_{9} = 80.9586747455212$$
$$x_{10} = 19.5722901693522$$
$$x_{11} = 93.5250453598804$$
$$x_{12} = -50.9882167052501$$
$$x_{13} = 32.1386607837113$$
$$x_{14} = 82.404143241148$$
$$x_{15} = -80.9586747455212$$
$$x_{16} = 420.250681333219$$
$$x_{17} = 49.5427482096233$$
$$x_{18} = 38.4218460908909$$
$$x_{19} = 76.1209579339685$$
$$x_{20} = 25.8554754765318$$
$$x_{21} = -101.253699162687$$
$$x_{22} = 18.1268216737253$$
$$x_{23} = 5.56045105936617$$
$$x_{24} = -93.5250453598804$$
$$x_{25} = -32.1386607837113$$
$$x_{26} = -76.1209579339685$$
$$x_{27} = 94.9705138555072$$
$$x_{28} = 50.9882167052501$$
$$x_{29} = 30.6931922880845$$
$$x_{30} = -36.9763775952641$$
$$x_{31} = -19.5722901693522$$
$$x_{32} = 0.722734247813416$$
$$x_{33} = -63.5545873196093$$
$$x_{34} = 16770.5443191101$$
$$x_{35} = -99.80823066706$$
$$x_{36} = 57.2714020124297$$
$$x_{37} = -74.6754894383416$$
$$x_{38} = -44.7050313980705$$
$$x_{39} = -49.5427482096233$$
$$x_{40} = 62.1091188239824$$
$$x_{41} = 7.005919554993$$
$$x_{42} = -55.8259335168029$$
$$x_{43} = 44.7050313980705$$
$$x_{44} = 36.9763775952641$$
$$x_{45} = -0.722734247813416$$
$$x_{46} = -7.005919554993$$
$$x_{47} = 24.4100069809049$$
$$x_{48} = -38.4218460908909$$
$$x_{49} = 63.5545873196093$$
$$x_{50} = 88.6873285483276$$
$$x_{51} = -69.8377726267889$$
$$x_{52} = -82.404143241148$$
$$x_{53} = 11.8436363665458$$
$$x_{54} = -87.2418600527008$$
$$x_{55} = -30.6931922880845$$
$$x_{56} = -5.56045105936617$$
$$x_{57} = -25.8554754765318$$
$$x_{58} = -57.2714020124297$$
$$x_{59} = -68.392304131162$$
$$x_{60} = 55.8259335168029$$
$$x_{61} = -88.6873285483276$$
$$x_{62} = 68.392304131162$$
$$x_{63} = 157.802366927303$$
$$x_{64} = 69.8377726267889$$
$$x_{65} = -62.1091188239824$$
$$x_{66} = 99.80823066706$$
$$x_{67} = -11.8436363665458$$
$$x_{68} = -24.4100069809049$$