El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\left(\frac{\cos{\left(x \right)}}{8} + \cos{\left(3 x \right)}\right) + \sin{\left(3 x \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución numérica$$x_{1} = 84.5329364151724$$
$$x_{2} = 100.240899683121$$
$$x_{3} = -53.6971403427785$$
$$x_{4} = -29.5754814187805$$
$$x_{5} = -88.2546595322662$$
$$x_{6} = -40.0348898918404$$
$$x_{7} = -1.30114753647236$$
$$x_{8} = 260.462125016201$$
$$x_{9} = -9.71484319252137$$
$$x_{10} = 52.1059275745541$$
$$x_{11} = 98.1951868661105$$
$$x_{12} = -90.3003723492771$$
$$x_{13} = 49.9754172256847$$
$$x_{14} = -39.0002593795499$$
$$x_{15} = -59.9803256499581$$
$$x_{16} = 87.6745290687622$$
$$x_{17} = 10.2305925655963$$
$$x_{18} = 3.9474072584167$$
$$x_{19} = -7.58433284365195$$
$$x_{20} = -68.3092237741485$$
$$x_{21} = 21.7010833433766$$
$$x_{22} = -74.5924090813281$$
$$x_{23} = -75.688288917907$$
$$x_{24} = -5.47737070235268$$
$$x_{25} = 34.2674539577357$$
$$x_{26} = 47.9297044086738$$
$$x_{27} = -84.0171870420975$$
$$x_{28} = 23.831593692246$$
$$x_{29} = 69.9208529838023$$
$$x_{30} = 54.2128897158534$$
$$x_{31} = 56.2586025328643$$
$$x_{32} = 74.0970761496827$$
$$x_{33} = 30.1147789994256$$
$$x_{34} = 25.9385558335452$$
$$x_{35} = 36.3979643066052$$
$$x_{36} = -95.5489271441662$$
$$x_{37} = 8.12363042429702$$
$$x_{38} = 41.6465191014942$$
$$x_{39} = 76.2040382909819$$
$$x_{40} = 71.9665658008133$$
$$x_{41} = 43.6922319185051$$
$$x_{42} = -100.821030146625$$
$$x_{43} = 27.9842686505561$$
$$x_{44} = -22.2812138068805$$
$$x_{45} = -71.4508164277383$$
$$x_{46} = -81.9714742250866$$
$$x_{47} = -79.8409638762172$$
$$x_{48} = 58.3891128817337$$
$$x_{49} = 91.9120015589309$$
$$x_{50} = -44.2723623820091$$
$$x_{51} = -13.8675181508315$$
$$x_{52} = 82.4872235981615$$
$$x_{53} = 1.84044511711743$$
$$x_{54} = -55.7428531597894$$
$$x_{55} = 19.6553705263657$$
$$x_{56} = 62.5417878400439$$
$$x_{57} = -26.4338887651907$$
$$x_{58} = -73.5577785690376$$
$$x_{59} = -62.026038466969$$
$$x_{60} = 12.2763053826072$$
$$x_{61} = -0.290065231751989$$
$$x_{62} = 38.5049264479044$$
$$x_{63} = -47.4139550355989$$
$$x_{64} = -31.7059917676499$$
$$x_{65} = 14.4068157314766$$
$$x_{66} = -18.0437413167119$$
$$x_{67} = 96.0882247248112$$
$$x_{68} = 89.8050394176316$$
$$x_{69} = 78.2497511079928$$
$$x_{70} = -99.7251503100465$$
$$x_{71} = -97.6794374930356$$
$$x_{72} = -64.1330006082682$$
$$x_{73} = -35.8586667259601$$
$$x_{74} = -37.9891770748295$$
$$x_{75} = 60.496075023033$$
$$x_{76} = -57.8498153010886$$
$$x_{77} = 67.8138908425031$$
$$x_{78} = -15.998028499701$$
$$x_{79} = 45.8227422673745$$
$$x_{80} = -42.1418520331397$$
$$x_{81} = -93.4419650028669$$
$$x_{82} = 32.2217411407248$$
$$x_{83} = -33.7517045846608$$
$$x_{84} = 80.3802614568623$$
$$x_{85} = -11.7605560095323$$
$$x_{86} = -66.2635109571376$$
$$x_{87} = -49.4596678526098$$
$$x_{88} = -51.5666299939091$$
$$x_{89} = -20.1507034580111$$
$$x_{90} = -52.6012605061996$$
$$x_{91} = -86.1241491833968$$
$$x_{92} = 65.6833804936337$$
$$x_{93} = 5.9931200754276$$
$$x_{94} = 16.5137778727759$$
$$x_{95} = 314.965079963806$$
$$x_{96} = -27.4685192774812$$
$$x_{97} = -41.1307697284193$$
$$x_{98} = 93.9577143759418$$
$$x_{99} = -77.7340017349179$$