El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\sqrt{2} \cos{\left(4 x \right)} + \sqrt{2} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = \frac{\pi}{4}$$
Solución numérica$$x_{1} = -33.7721211587531$$
$$x_{2} = 99.7455668738049$$
$$x_{3} = 46.3384915861013$$
$$x_{4} = 93.462381626966$$
$$x_{5} = 62.0464548185713$$
$$x_{6} = -98.1747703186947$$
$$x_{7} = 3.92699087784889$$
$$x_{8} = 32.2013247418649$$
$$x_{9} = 0.785398118063847$$
$$x_{10} = 24.347343006498$$
$$x_{11} = -13.3517688688202$$
$$x_{12} = -27.4889358330644$$
$$x_{13} = 5.49778696422816$$
$$x_{14} = 10.2101761577675$$
$$x_{15} = 19.6349541951516$$
$$x_{16} = -76.1836217409515$$
$$x_{17} = 18.0641575853046$$
$$x_{18} = 77.7544182976932$$
$$x_{19} = -63.6172513104641$$
$$x_{20} = 90.3207887457625$$
$$x_{21} = 47.9092880382216$$
$$x_{22} = 85.6083999066255$$
$$x_{23} = -11.780972425667$$
$$x_{24} = 63.6172513369298$$
$$x_{25} = -98.1747705479865$$
$$x_{26} = 16.4933613203203$$
$$x_{27} = -35.3429174368834$$
$$x_{28} = -57.3340660035604$$
$$x_{29} = 76.1836219127145$$
$$x_{30} = -41.6261027314388$$
$$x_{31} = 22.7765470504813$$
$$x_{32} = -24.3473429491357$$
$$x_{33} = 84.0376034192262$$
$$x_{34} = -93.4623815613976$$
$$x_{35} = -18.0641577028072$$
$$x_{36} = 60.4756584745212$$
$$x_{37} = -54.1924731634027$$
$$x_{38} = 98.1747704999445$$
$$x_{39} = -40.0553062838236$$
$$x_{40} = -68.3296400953708$$
$$x_{41} = 96.6039739860399$$
$$x_{42} = -16.4933615591447$$
$$x_{43} = -82.4668071752083$$
$$x_{44} = 55.7632697213615$$
$$x_{45} = -19.6349541522704$$
$$x_{46} = -49.4800844094223$$
$$x_{47} = 71.4712325592813$$
$$x_{48} = 69.9004366179912$$
$$x_{49} = -84.0376034471411$$
$$x_{50} = -33.7721210085549$$
$$x_{51} = 40.055306209136$$
$$x_{52} = -62.0464548652478$$
$$x_{53} = 27.4889354808973$$
$$x_{54} = -55.763269590985$$
$$x_{55} = -46.3384915220366$$
$$x_{56} = 25.918139458182$$
$$x_{57} = -79.325214568582$$
$$x_{58} = 91.8915851975093$$
$$x_{59} = -99.7455667547305$$
$$x_{60} = 82.4668070519044$$
$$x_{61} = -32.2013245860493$$
$$x_{62} = 66.7588441131007$$
$$x_{63} = -71.4712329855388$$
$$x_{64} = 54.1924733267788$$
$$x_{65} = 8.63937970041344$$
$$x_{66} = -0.785398166130751$$
$$x_{67} = 49.4800839996026$$
$$x_{68} = 68.3296401658547$$
$$x_{69} = 33.7721211448164$$
$$x_{70} = -465.741111003319$$
$$x_{71} = 52.6216768417318$$
$$x_{72} = -85.608399889346$$
$$x_{73} = 2.35619442704144$$
$$x_{74} = 88.7499926302988$$
$$x_{75} = 74.6128254135616$$
$$x_{76} = 41.6261027663993$$
$$x_{77} = -90.3207886690967$$
$$x_{78} = 44.7676955973049$$
$$x_{79} = -10.210176008893$$
$$x_{80} = -5.49778725647941$$
$$x_{81} = -19.6349539733882$$
$$x_{82} = -3.92699105526517$$
$$x_{83} = -77.7544181730257$$
$$x_{84} = 30.6305282706443$$
$$x_{85} = -2.35619437671896$$
$$x_{86} = 11.7809725680634$$
$$x_{87} = -38.4845100906754$$
$$x_{88} = 38.4845098973237$$
$$x_{89} = -60.4756586297418$$