El gráfico de la función cruce el eje T con f = 0
o sea hay que resolver la ecuación:
$$3 e^{- t} \sin{\left(2 t \right)} + e^{- t} \cos{\left(2 t \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje T:
Solución analítica$$t_{1} = - \frac{\operatorname{atan}{\left(\frac{1}{3} \right)}}{2}$$
Solución numérica$$t_{1} = -23.7228201791218$$
$$t_{2} = 94.0869043304955$$
$$t_{3} = 26.5426622783149$$
$$t_{4} = 4.55151370318637$$
$$t_{5} = 86.232922696521$$
$$t_{6} = 24.97186595152$$
$$t_{7} = 12.4054953371609$$
$$t_{8} = 95.6577006572904$$
$$t_{9} = -17.4396348719422$$
$$t_{10} = 34.3966439122894$$
$$t_{11} = -25.2936165059167$$
$$t_{12} = 90.9453116769057$$
$$t_{13} = 65.8125704481873$$
$$t_{14} = 51.6754035070333$$
$$t_{15} = 2.98071737639147$$
$$t_{16} = 18.6886806443404$$
$$t_{17} = -22.1520238523269$$
$$t_{18} = 78.3789410625465$$
$$t_{19} = -1.73167160399322$$
$$t_{20} = 56.387792487418$$
$$t_{21} = 21.8302732979302$$
$$t_{22} = 50.1046071802384$$
$$t_{23} = 35.9674402390843$$
$$t_{24} = 48.5338108534435$$
$$t_{25} = 68.9541631017771$$
$$t_{26} = 79.9497373893414$$
$$t_{27} = -30.0060054863014$$
$$t_{28} = 46.9630145266486$$
$$t_{29} = -8.0148569111728$$
$$t_{30} = 6.12231002998127$$
$$t_{31} = 10.834699010366$$
$$t_{32} = 40.679829219469$$
$$t_{33} = 92.5161080037006$$
$$t_{34} = 110.460422077029$$
$$t_{35} = 76.8081447357516$$
$$t_{36} = -14.2980422183524$$
$$t_{37} = 64.2417741213924$$
$$t_{38} = 20.2594769711353$$
$$t_{39} = 7.69310635677616$$
$$t_{40} = 32.8258475854945$$
$$t_{41} = 43.8214218730588$$
$$t_{42} = -9.5856532379677$$
$$t_{43} = 42.2506255462639$$
$$t_{44} = -15.8688385451473$$
$$t_{45} = -11.1564495647626$$
$$t_{46} = 54.8169961606231$$
$$t_{47} = 72.0957557553669$$
$$t_{48} = 73.6665520821618$$
$$t_{49} = 98.7992933108802$$
$$t_{50} = -3.30246793078811$$
$$t_{51} = 45.3922181998537$$
$$t_{52} = 70.524959428572$$
$$t_{53} = 28.1134586051098$$
$$t_{54} = 87.8037190233159$$
$$t_{55} = 84.6621263697261$$
$$t_{56} = -0.160875277198321$$
$$t_{57} = 13.9762916639557$$
$$t_{58} = 100.370089637675$$
$$t_{59} = 29.6842549319047$$
$$t_{60} = 57.9585888142129$$
$$t_{61} = 62.6709777945975$$