Graph of the function intersects the axis X at f = 0
so we need to solve the equation:
$$3 \sin{\left(x \right)} + 4 \cos{\left(x \right)} = 0$$
Solve this equationThe points of intersection with the axis X:
Analytical solution$$x_{1} = - \operatorname{atan}{\left(\frac{4}{3} \right)}$$
Numerical solution$$x_{1} = -38.6264070610791$$
$$x_{2} = 83.8957064289228$$
$$x_{3} = -29.2016291003098$$
$$x_{4} = 55.6213725466147$$
$$x_{5} = -35.4848144074893$$
$$x_{6} = 24.2054460107167$$
$$x_{7} = 77.6125211217432$$
$$x_{8} = -88.8918895185158$$
$$x_{9} = -26.06003644672$$
$$x_{10} = -19.7768511395404$$
$$x_{11} = -76.3255189041567$$
$$x_{12} = 27.3470386643065$$
$$x_{13} = -7.2104805251812$$
$$x_{14} = -73.1839262505669$$
$$x_{15} = -32.3432217538995$$
$$x_{16} = -4.06888787159141$$
$$x_{17} = 17.9222607035371$$
$$x_{18} = 90.1788917361024$$
$$x_{19} = 74.4709284681534$$
$$x_{20} = 96.462077043282$$
$$x_{21} = -0.927295218001612$$
$$x_{22} = 11.6390753963576$$
$$x_{23} = 93.3204843896922$$
$$x_{24} = -51.1927776754383$$
$$x_{25} = 87.0372990825126$$
$$x_{26} = 109.028447657641$$
$$x_{27} = -44.9095923682587$$
$$x_{28} = -92.0334821721056$$
$$x_{29} = 68.1877431609738$$
$$x_{30} = 8.49748274276777$$
$$x_{31} = -79.4671115577464$$
$$x_{32} = 52.4797798930249$$
$$x_{33} = 21.0638533571269$$
$$x_{34} = 5.35589008917797$$
$$x_{35} = -48.0511850218485$$
$$x_{36} = 2.21429743558818$$
$$x_{37} = 65.046150507384$$
$$x_{38} = 168.718708075847$$
$$x_{39} = -66.9007409433873$$
$$x_{40} = -710.927234929295$$
$$x_{41} = 61.9045578537943$$
$$x_{42} = 43.0550019322555$$
$$x_{43} = 49.3381872394351$$
$$x_{44} = -70.0423335969771$$
$$x_{45} = 58.7629652002045$$
$$x_{46} = -41.7679997146689$$
$$x_{47} = 71.3293358145636$$
$$x_{48} = -85.750296864926$$
$$x_{49} = -10.352073178771$$
$$x_{50} = 33.6302239714861$$
$$x_{51} = 36.7718166250759$$
$$x_{52} = 99.6036696968718$$
$$x_{53} = -82.6087042113362$$
$$x_{54} = -54.3343703290281$$
$$x_{55} = -63.7591482897975$$
$$x_{56} = -57.4759629826179$$
$$x_{57} = 39.9134092786657$$
$$x_{58} = -98.3166674792852$$
$$x_{59} = -22.9184437931302$$
$$x_{60} = 14.7806680499474$$
$$x_{61} = 30.4886313178963$$
$$x_{62} = 46.1965945858453$$
$$x_{63} = -95.1750748256954$$
$$x_{64} = -60.6175556362077$$
$$x_{65} = 80.754113775333$$
$$x_{66} = -13.4936658323608$$
$$x_{67} = -16.6352584859506$$