El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\left(-3\right) \cos{\left(2 x - \frac{\pi}{3} \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = - \frac{\pi}{12}$$
$$x_{2} = \frac{5 \pi}{12}$$
Solución numérica$$x_{1} = -11.2573736753634$$
$$x_{2} = -67.8060414399797$$
$$x_{3} = 4.45058959258554$$
$$x_{4} = -52.0980781720307$$
$$x_{5} = 78.2780169519457$$
$$x_{6} = 57.857664703612$$
$$x_{7} = 20.1585528605345$$
$$x_{8} = 29.5833308213039$$
$$x_{9} = 56.2868683768171$$
$$x_{10} = -80.3724120543389$$
$$x_{11} = 28.012534494509$$
$$x_{12} = -66.2352451131848$$
$$x_{13} = 64.1408500107916$$
$$x_{14} = 2307.2380046739$$
$$x_{15} = 18.5877565337396$$
$$x_{16} = -45.8148928648512$$
$$x_{17} = -88.2263936883134$$
$$x_{18} = 26.4417381677141$$
$$x_{19} = 42.1497014356631$$
$$x_{20} = -30.1069295969022$$
$$x_{21} = -61.5228561328001$$
$$x_{22} = -44.2440965380563$$
$$x_{23} = -83.5140047079287$$
$$x_{24} = -77.2308194007491$$
$$x_{25} = -0.261799387799149$$
$$x_{26} = -14.3989663289532$$
$$x_{27} = -58.3812634792103$$
$$x_{28} = 6.02138591938044$$
$$x_{29} = -36.3901149040818$$
$$x_{30} = -17.540558982543$$
$$x_{31} = -9.68657734856853$$
$$x_{32} = -31.6777259236971$$
$$x_{33} = 92.4151838930998$$
$$x_{34} = 54.7160720500222$$
$$x_{35} = 100.269165527074$$
$$x_{36} = 13.8753675533549$$
$$x_{37} = -89.7971900151083$$
$$x_{38} = 32.7249234748937$$
$$x_{39} = 35.8665161284835$$
$$x_{40} = 12.30457122656$$
$$x_{41} = -81.9432083811338$$
$$x_{42} = 43.720497762458$$
$$x_{43} = 79.8488132787406$$
$$x_{44} = 84.5612022591253$$
$$x_{45} = -8.11578102177363$$
$$x_{46} = 40.5789051088682$$
$$x_{47} = 48.4328867428426$$
$$x_{48} = 10.7337748997651$$
$$x_{49} = -25.3945406165175$$
$$x_{50} = 103.410758180664$$
$$x_{51} = -97.6511716490827$$
$$x_{52} = -59.9520598060052$$
$$x_{53} = -108.646745936647$$
$$x_{54} = 62.5700536839967$$
$$x_{55} = 76.7072206251508$$
$$x_{56} = -91.3679863419031$$
$$x_{57} = 21.7293491873294$$
$$x_{58} = -37.9609112308767$$
$$x_{59} = -94.5095789954929$$
$$x_{60} = 34.2957198016886$$
$$x_{61} = 98.6983692002793$$
$$x_{62} = 95.5567765466895$$
$$x_{63} = -23.8237442897226$$
$$x_{64} = 71.9948316447661$$
$$x_{65} = 70.4240353179712$$
$$x_{66} = -1.83259571459405$$
$$x_{67} = -55.2396708256205$$
$$x_{68} = -33.248522250492$$
$$x_{69} = 93.9859802198946$$
$$x_{70} = 7.59218224617533$$
$$x_{71} = 50.0036830696375$$
$$x_{72} = 86.1319985859202$$
$$x_{73} = 87.7027949127151$$
$$x_{74} = -75.6600230739542$$
$$x_{75} = 210.224908402717$$
$$x_{76} = -53.6688744988256$$
$$x_{77} = -39.5317075576716$$
$$x_{78} = 51.5744793964324$$
$$x_{79} = 73.565627971561$$
$$x_{80} = -69.3768377667746$$
$$x_{81} = -47.3856891916461$$
$$x_{82} = -96.0803753222878$$
$$x_{83} = -15.9697626557481$$
$$x_{84} = -72.5184304203644$$
$$x_{85} = 65.7116463375865$$
$$x_{86} = -22.2529479629277$$
$$x_{87} = -3.40339204138894$$
$$x_{88} = -74.0892267471593$$