El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$- \cos{\left(x \right)} + \tan{\left(x \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = - i \log{\left(- \frac{\sqrt{2} \sqrt{-1 + \sqrt{5}}}{2} - \frac{i \left(1 - \sqrt{5}\right)}{2} \right)}$$
$$x_{2} = - i \log{\left(\frac{\sqrt{2} \sqrt{-1 + \sqrt{5}}}{2} - \frac{i \left(1 - \sqrt{5}\right)}{2} \right)}$$
Solución numérica$$x_{1} = 101.197204347366$$
$$x_{2} = -18.1833164890462$$
$$x_{3} = -66.6396851578782$$
$$x_{4} = -87.2983548680217$$
$$x_{5} = 90.4399475216115$$
$$x_{6} = -68.4487989464829$$
$$x_{7} = -43.3160577177646$$
$$x_{8} = 32.0821659683904$$
$$x_{9} = -54.073314543519$$
$$x_{10} = 71.5903916000727$$
$$x_{11} = -28.9405733148007$$
$$x_{12} = -41.5069439291598$$
$$x_{13} = 0.666239432492515$$
$$x_{14} = 2.47535322109728$$
$$x_{15} = 27.6080944498156$$
$$x_{16} = -49.5992430249442$$
$$x_{17} = -35.2237586219802$$
$$x_{18} = 84.1567622144319$$
$$x_{19} = 94.9140190401863$$
$$x_{20} = -16.3742027004415$$
$$x_{21} = 82.3476484258271$$
$$x_{22} = 59.0240209857136$$
$$x_{23} = -10.0910173932619$$
$$x_{24} = -62.1656136393034$$
$$x_{25} = 40.1744650641748$$
$$x_{26} = -5.61694587468707$$
$$x_{27} = -91.7724263865965$$
$$x_{28} = 19.5157953540313$$
$$x_{29} = 50.9317218899292$$
$$x_{30} = 52.740835678534$$
$$x_{31} = 96.7231328287911$$
$$x_{32} = -30.7496871034054$$
$$x_{33} = -22.6573880076211$$
$$x_{34} = 65.3072062928931$$
$$x_{35} = 13.2326100468517$$
$$x_{36} = 46.4576503713544$$
$$x_{37} = 44.6485365827496$$
$$x_{38} = 57.2149071971088$$
$$x_{39} = 6.9494247396721$$
$$x_{40} = 15.0417238354565$$
$$x_{41} = 38.36535127557$$
$$x_{42} = -74.7319842536625$$
$$x_{43} = -99.8647254823809$$
$$x_{44} = -98.0556116937761$$
$$x_{45} = -85.4892410794169$$
$$x_{46} = -93.5815401752013$$
$$x_{47} = -3.80783208608231$$
$$x_{48} = -81.0151695608421$$
$$x_{49} = 33.8912797569952$$
$$x_{50} = 25.7989806612109$$
$$x_{51} = -47.7901292363394$$
$$x_{52} = -60.3564998506986$$
$$x_{53} = -11.9001311818667$$
$$x_{54} = 69.781277811468$$
$$x_{55} = -72.9228704650578$$
$$x_{56} = 21.324909142636$$
$$x_{57} = -24.4665017962258$$
$$x_{58} = -37.032872410585$$
$$x_{59} = 77.8735769072523$$
$$x_{60} = 76.0644631186476$$
$$x_{61} = -55.8824283321238$$
$$x_{62} = 8.75853852827686$$
$$x_{63} = 88.6308337330067$$
$$x_{64} = -79.2060557722373$$
$$x_{65} = 63.4980925042884$$