El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$1 - 3 \cos{\left(x - \frac{\pi}{2} \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = \pi - \operatorname{asin}{\left(\frac{1}{3} \right)}$$
$$x_{2} = \operatorname{asin}{\left(\frac{1}{3} \right)}$$
Solución numérica$$x_{1} = 44.3221340597112$$
$$x_{2} = -18.5097190120846$$
$$x_{3} = 19.1893928309929$$
$$x_{4} = -49.9256455479826$$
$$x_{5} = 53.0672382015724$$
$$x_{6} = -100.191128005419$$
$$x_{7} = 75.7380605956092$$
$$x_{8} = 12.9062075238133$$
$$x_{9} = -66.3132826348398$$
$$x_{10} = 78.1999794302907$$
$$x_{11} = -62.4920161623417$$
$$x_{12} = 2.80175574413567$$
$$x_{13} = 25.4725781381725$$
$$x_{14} = 46.7840528943928$$
$$x_{15} = -24.7929043192642$$
$$x_{16} = 6.62302221663371$$
$$x_{17} = -85.1628385563785$$
$$x_{18} = 82.0212459027887$$
$$x_{19} = -72.5964679420194$$
$$x_{20} = -12.2265337049051$$
$$x_{21} = -53.7469120204806$$
$$x_{22} = -9.7646148702235$$
$$x_{23} = 50.6053193668908$$
$$x_{24} = 21.6513116656744$$
$$x_{25} = -81.3415720838805$$
$$x_{26} = -34.8973560989418$$
$$x_{27} = 90.7663500446499$$
$$x_{28} = -91.4460238635581$$
$$x_{29} = 94.5876165171479$$
$$x_{30} = -5.94334839772546$$
$$x_{31} = -87.6247573910601$$
$$x_{32} = -68.7752014695213$$
$$x_{33} = 59.350423508752$$
$$x_{34} = 172.447759037984$$
$$x_{35} = 34.2176822800336$$
$$x_{36} = -75.0583867767009$$
$$x_{37} = 15.3681263584948$$
$$x_{38} = -41.1805414061214$$
$$x_{39} = 63.17168998125$$
$$x_{40} = -56.2088308551622$$
$$x_{41} = 100.870801824328$$
$$x_{42} = 27.934496972854$$
$$x_{43} = -31.0760896264438$$
$$x_{44} = 9.08494105131526$$
$$x_{45} = -116.578765092276$$
$$x_{46} = 65.6336088159315$$
$$x_{47} = 84.4831647374703$$
$$x_{48} = -3.48142956304392$$
$$x_{49} = -93.9079426982397$$
$$x_{50} = -22.3309854845827$$
$$x_{51} = -78.879653249199$$
$$x_{52} = -16.0478001774031$$
$$x_{53} = 56.8885046740704$$
$$x_{54} = -47.463726713301$$
$$x_{55} = -60.0300973276602$$
$$x_{56} = 71.9167941231111$$
$$x_{57} = 97.0495353518295$$
$$x_{58} = 88.3044312099683$$
$$x_{59} = 31.7557634453521$$
$$x_{60} = -43.642460240803$$
$$x_{61} = 40.5008675872132$$
$$x_{62} = -97.7292091707377$$
$$x_{63} = -28.6141707917623$$
$$x_{64} = 69.4548752884296$$
$$x_{65} = 0.339836909454122$$
$$x_{66} = -37.3592749336234$$
$$x_{67} = 38.0389487525316$$