El gráfico de la función cruce el eje T con f = 0
o sea hay que resolver la ecuación:
$$2 \cos{\left(t \right)} - \cos{\left(3 t \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje T:
Solución analítica$$t_{1} = - \frac{\pi}{2}$$
$$t_{2} = \frac{\pi}{2}$$
Solución numérica$$t_{1} = 14.1371669411541$$
$$t_{2} = 73.8274273593601$$
$$t_{3} = 89.5353906273091$$
$$t_{4} = -23.5619449019235$$
$$t_{5} = -86.3937979737193$$
$$t_{6} = 20.4203522483337$$
$$t_{7} = -64.4026493985908$$
$$t_{8} = 42.4115008234622$$
$$t_{9} = -42.4115008234622$$
$$t_{10} = -29.845130209103$$
$$t_{11} = 51.8362787842316$$
$$t_{12} = 1.5707963267949$$
$$t_{13} = -67.5442420521806$$
$$t_{14} = -36.1283155162826$$
$$t_{15} = 45.553093477052$$
$$t_{16} = -80.1106126665397$$
$$t_{17} = 86.3937979737193$$
$$t_{18} = -73.8274273593601$$
$$t_{19} = 64.4026493985908$$
$$t_{20} = 95.8185759344887$$
$$t_{21} = -1.5707963267949$$
$$t_{22} = -10.9955742875643$$
$$t_{23} = -20.4203522483337$$
$$t_{24} = 142.942465738336$$
$$t_{25} = 92.6769832808989$$
$$t_{26} = 36.1283155162826$$
$$t_{27} = -58.1194640914112$$
$$t_{28} = 4.71238898038469$$
$$t_{29} = 1547.23438189297$$
$$t_{30} = -95.8185759344887$$
$$t_{31} = -51.8362787842316$$
$$t_{32} = 23.5619449019235$$
$$t_{33} = 67.5442420521806$$
$$t_{34} = -72044.5735284479$$
$$t_{35} = -14.1371669411541$$
$$t_{36} = 76.9690200129499$$
$$t_{37} = 80.1106126665397$$
$$t_{38} = -7.85398163397448$$
$$t_{39} = 7.85398163397448$$
$$t_{40} = 58.1194640914112$$
$$t_{41} = -45.553093477052$$
$$t_{42} = 70.6858347057703$$
$$t_{43} = 259.181393921158$$
$$t_{44} = 26.7035375555132$$
$$t_{45} = -89.5353906273091$$
$$t_{46} = 10.9955742875643$$
$$t_{47} = -54.9778714378214$$
$$t_{48} = 29.845130209103$$
$$t_{49} = -287.455727803466$$
$$t_{50} = 111.526539202438$$