Graph of the function intersects the axis X at f = 0
so we need to solve the equation:
$$- 3 \sin{\left(x \right)} + 2 \cos{\left(x \right)} = 0$$
Solve this equationThe points of intersection with the axis X:
Analytical solution$$x_{1} = \operatorname{atan}{\left(\frac{2}{3} \right)}$$
Numerical solution$$x_{1} = -27.6863312787606$$
$$x_{2} = -43.3942945467095$$
$$x_{3} = 53.9950777145741$$
$$x_{4} = 75.9862262897026$$
$$x_{5} = -87.3765916969666$$
$$x_{6} = 28.8623364858557$$
$$x_{7} = 101.118967518421$$
$$x_{8} = 47.7118924073945$$
$$x_{9} = -93.6597770041462$$
$$x_{10} = 66.5614483289332$$
$$x_{11} = 32.0039291394455$$
$$x_{12} = -59.1022578146585$$
$$x_{13} = 16.2959658714965$$
$$x_{14} = 38.2871144466251$$
$$x_{15} = -99.9429623113258$$
$$x_{16} = -65.3854431218381$$
$$x_{17} = 57.1366703681638$$
$$x_{18} = -52.8190725074789$$
$$x_{19} = -8.83677535722181$$
$$x_{20} = 6.87118791072715$$
$$x_{21} = 91.6941895576516$$
$$x_{22} = -40.2527018931197$$
$$x_{23} = 0.588002603547568$$
$$x_{24} = -68.5270357754279$$
$$x_{25} = -84.2349990433768$$
$$x_{26} = -15.1199606644014$$
$$x_{27} = 10.0127805643169$$
$$x_{28} = -49.6774798538891$$
$$x_{29} = -62.2438504682483$$
$$x_{30} = -21.403145971581$$
$$x_{31} = -106.226147618505$$
$$x_{32} = 79.1278189432924$$
$$x_{33} = 182.800376511756$$
$$x_{34} = 85.411004250472$$
$$x_{35} = 94.8357822112414$$
$$x_{36} = 41.4287071002149$$
$$x_{37} = -5.69518270363202$$
$$x_{38} = -24.5447386251708$$
$$x_{39} = -81.0934063897871$$
$$x_{40} = 50.8534850609843$$
$$x_{41} = -30.8279239323504$$
$$x_{42} = 88.5525969040618$$
$$x_{43} = 72.8446336361128$$
$$x_{44} = -74.8102210826075$$
$$x_{45} = -18.2615533179912$$
$$x_{46} = -46.5358872002993$$
$$x_{47} = 242.490636929962$$
$$x_{48} = 69.703040982523$$
$$x_{49} = -2.55359005004223$$
$$x_{50} = 44.5702997538047$$
$$x_{51} = 25.7207438322659$$
$$x_{52} = 97.9773748648312$$
$$x_{53} = -77.9518137361973$$
$$x_{54} = -71.6686284290177$$
$$x_{55} = 13.1543732179067$$
$$x_{56} = -37.11110923953$$
$$x_{57} = 82.2694115968822$$
$$x_{58} = -11.9783680108116$$
$$x_{59} = 60.2782630217536$$
$$x_{60} = 3.72959525713736$$
$$x_{61} = -90.5181843505564$$
$$x_{62} = 35.1455217930353$$
$$x_{63} = -55.9606651610687$$
$$x_{64} = -96.801369657736$$
$$x_{65} = 19.4375585250863$$
$$x_{66} = 63.4198556753434$$
$$x_{67} = 22.5791511786761$$
$$x_{68} = -33.9695165859402$$