Graph of the function intersects the axis X at f = 0
so we need to solve the equation:
$$3 \sin{\left(x \right)} + 1 = 0$$
Solve this equationThe points of intersection with the axis X:
Analytical solution$$x_{1} = \operatorname{asin}{\left(\frac{1}{3} \right)} + \pi$$
$$x_{2} = - \operatorname{asin}{\left(\frac{1}{3} \right)}$$
Numerical solution$$x_{1} = 24.7929043192642$$
$$x_{2} = 53.7469120204806$$
$$x_{3} = 81.3415720838805$$
$$x_{4} = -358.481399418691$$
$$x_{5} = 97.7292091707377$$
$$x_{6} = -25.4725781381725$$
$$x_{7} = 62.4920161623417$$
$$x_{8} = 91.4460238635581$$
$$x_{9} = 16.0478001774031$$
$$x_{10} = 31.0760896264438$$
$$x_{11} = -59.350423508752$$
$$x_{12} = -75.7380605956092$$
$$x_{13} = -82.0212459027887$$
$$x_{14} = -12.9062075238133$$
$$x_{15} = -90.7663500446499$$
$$x_{16} = -0.339836909454122$$
$$x_{17} = -40.5008675872132$$
$$x_{18} = -19.1893928309929$$
$$x_{19} = -15.3681263584948$$
$$x_{20} = 41.1805414061214$$
$$x_{21} = -27.934496972854$$
$$x_{22} = -78.1999794302907$$
$$x_{23} = 72.5964679420194$$
$$x_{24} = 22.3309854845827$$
$$x_{25} = 37.3592749336234$$
$$x_{26} = -31.7557634453521$$
$$x_{27} = 78.879653249199$$
$$x_{28} = 28.6141707917623$$
$$x_{29} = 144.173425155676$$
$$x_{30} = -21.6513116656744$$
$$x_{31} = 93.9079426982397$$
$$x_{32} = 68.7752014695213$$
$$x_{33} = 66.3132826348398$$
$$x_{34} = -69.4548752884296$$
$$x_{35} = 47.463726713301$$
$$x_{36} = -50.6053193668908$$
$$x_{37} = 60.0300973276602$$
$$x_{38} = 9.7646148702235$$
$$x_{39} = -71.9167941231111$$
$$x_{40} = 3386.29704366034$$
$$x_{41} = -2.80175574413567$$
$$x_{42} = 85.1628385563785$$
$$x_{43} = -53.0672382015724$$
$$x_{44} = -63.17168998125$$
$$x_{45} = 56.2088308551622$$
$$x_{46} = -9.08494105131526$$
$$x_{47} = 34.8973560989418$$
$$x_{48} = -34.2176822800336$$
$$x_{49} = 12.2265337049051$$
$$x_{50} = 345.235354985423$$
$$x_{51} = -56.8885046740704$$
$$x_{52} = 75.0583867767009$$
$$x_{53} = -44.3221340597112$$
$$x_{54} = -65.6336088159315$$
$$x_{55} = 100.191128005419$$
$$x_{56} = 87.6247573910601$$
$$x_{57} = -46.7840528943928$$
$$x_{58} = -38.0389487525316$$
$$x_{59} = -97.0495353518295$$
$$x_{60} = -94.5876165171479$$
$$x_{61} = 18.5097190120846$$
$$x_{62} = 301.253057835166$$
$$x_{63} = 49.9256455479826$$
$$x_{64} = 43.642460240803$$
$$x_{65} = -88.3044312099683$$
$$x_{66} = -84.4831647374703$$
$$x_{67} = -100.870801824328$$
$$x_{68} = 5.94334839772546$$
$$x_{69} = 3.48142956304392$$
$$x_{70} = -6.62302221663371$$