El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\frac{4 \left(\left(- \cos{\left(\pi x \right)} - \frac{\cos{\left(3 \pi x \right)}}{9}\right) + \frac{\cos{\left(2 \pi x \right)}}{4}\right)}{\pi^{2}} + \frac{1}{3} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución numérica$$x_{1} = -73.9097275654084$$
$$x_{2} = -7.90972756540839$$
$$x_{3} = 46.0902724345916$$
$$x_{4} = 96.0902724345916$$
$$x_{5} = 92.0902724345916$$
$$x_{6} = 36.0902724345916$$
$$x_{7} = 64.0902724345916$$
$$x_{8} = 8.09027243459161$$
$$x_{9} = -85.9097275654084$$
$$x_{10} = 18.0902724345916$$
$$x_{11} = 68.0902724345916$$
$$x_{12} = 10.0902724345916$$
$$x_{13} = -61.9097275654084$$
$$x_{14} = 78.0902724345916$$
$$x_{15} = 76.0902724345916$$
$$x_{16} = 82.0902724345916$$
$$x_{17} = -63.9097275654084$$
$$x_{18} = -49.9097275654084$$
$$x_{19} = 22.0902724345916$$
$$x_{20} = 100.090272434592$$
$$x_{21} = 32.0902724345916$$
$$x_{22} = 80.0902724345916$$
$$x_{23} = -27.9097275654084$$
$$x_{24} = 38.0902724345916$$
$$x_{25} = -59.9097275654084$$
$$x_{26} = 62.0902724345916$$
$$x_{27} = -81.9097275654084$$
$$x_{28} = 44.0902724345916$$
$$x_{29} = 48.0902724345916$$
$$x_{30} = 70.0902724345916$$
$$x_{31} = 2.09027243459161$$
$$x_{32} = 28.0902724345916$$
$$x_{33} = -43.9097275654084$$
$$x_{34} = -1.90972756540839$$
$$x_{35} = -97.9097275654084$$
$$x_{36} = 14.0902724345916$$
$$x_{37} = 20.0902724345916$$
$$x_{38} = 24.0902724345916$$
$$x_{39} = 88.0902724345916$$
$$x_{40} = -33.9097275654084$$
$$x_{41} = -41.9097275654084$$
$$x_{42} = 90.0902724345916$$
$$x_{43} = 52.0902724345916$$
$$x_{44} = 30.0902724345916$$
$$x_{45} = 94.0902724345916$$
$$x_{46} = 12.0902724345916$$
$$x_{47} = -83.9097275654084$$
$$x_{48} = -67.9097275654084$$
$$x_{49} = 58.0902724345916$$
$$x_{50} = -19.9097275654084$$
$$x_{51} = 74.0902724345916$$
$$x_{52} = 66.0902724345916$$
$$x_{53} = -55.9097275654084$$
$$x_{54} = -93.9097275654084$$
$$x_{55} = 16.0902724345916$$
$$x_{56} = 26.0902724345916$$
$$x_{57} = -65.9097275654084$$
$$x_{58} = -35.9097275654084$$
$$x_{59} = -91.9097275654084$$
$$x_{60} = -21.9097275654084$$
$$x_{61} = -99.9097275654084$$
$$x_{62} = 60.0902724345916$$
$$x_{63} = -11.9097275654084$$
$$x_{64} = -71.9097275654084$$
$$x_{65} = -51.9097275654084$$
$$x_{66} = -89.9097275654084$$
$$x_{67} = -31.9097275654084$$
$$x_{68} = 54.0902724345916$$
$$x_{69} = 0.0902724345916086$$
$$x_{70} = 56.0902724345916$$
$$x_{71} = 72.0902724345916$$
$$x_{72} = -5.90972756540839$$
$$x_{73} = -53.9097275654084$$
$$x_{74} = -95.9097275654084$$
$$x_{75} = 6.09027243459161$$
$$x_{76} = -37.9097275654084$$
$$x_{77} = -25.9097275654084$$
$$x_{78} = 86.0902724345916$$
$$x_{79} = -17.9097275654084$$
$$x_{80} = -57.9097275654084$$
$$x_{81} = -69.9097275654084$$
$$x_{82} = 4.09027243459161$$
$$x_{83} = 42.0902724345916$$
$$x_{84} = -47.9097275654084$$
$$x_{85} = -13.9097275654084$$
$$x_{86} = -39.9097275654084$$
$$x_{87} = 84.0902724345916$$
$$x_{88} = -9.90972756540839$$
$$x_{89} = 40.0902724345916$$
$$x_{90} = -23.9097275654084$$
$$x_{91} = 34.0902724345916$$
$$x_{92} = -87.9097275654084$$
$$x_{93} = 98.0902724345916$$
$$x_{94} = -29.9097275654084$$
$$x_{95} = -75.9097275654084$$
$$x_{96} = -79.9097275654084$$
$$x_{97} = -77.9097275654084$$
$$x_{98} = -15.9097275654084$$
$$x_{99} = -45.9097275654084$$
$$x_{100} = -3.90972756540839$$
$$x_{101} = 50.0902724345916$$