Graph of the function intersects the axis X at f = 0
so we need to solve the equation:
$$\cos^{3}{\left(2 x \right)} = 0$$
Solve this equationThe points of intersection with the axis X:
Analytical solution$$x_{1} = \frac{\pi}{4}$$
$$x_{2} = \frac{3 \pi}{4}$$
Numerical solution$$x_{1} = 22.7765299742415$$
$$x_{2} = -38.4844614652797$$
$$x_{3} = 40.0552901985337$$
$$x_{4} = -60.4756065596791$$
$$x_{5} = -55.7632661328603$$
$$x_{6} = 71.4712468772624$$
$$x_{7} = 49.4801084694813$$
$$x_{8} = -62.0464394517635$$
$$x_{9} = 18.0641405401649$$
$$x_{10} = 82.4667599080185$$
$$x_{11} = -40.0552881765552$$
$$x_{12} = -99.7455679128678$$
$$x_{13} = -65.1880051060871$$
$$x_{14} = 93.4623829732543$$
$$x_{15} = 0.785393273933224$$
$$x_{16} = 47.9093160339062$$
$$x_{17} = 38.4844600184581$$
$$x_{18} = 46.3384695953885$$
$$x_{19} = -84.0375908161324$$
$$x_{20} = -16.4933171765021$$
$$x_{21} = -3.9270084103161$$
$$x_{22} = 25.9181651117762$$
$$x_{23} = 76.1836370585162$$
$$x_{24} = 44.7676689135041$$
$$x_{25} = 66.758809738519$$
$$x_{26} = -33.7721152742823$$
$$x_{27} = -54.19242365084$$
$$x_{28} = -43.1968731975691$$
$$x_{29} = -47.9093039196703$$
$$x_{30} = -18.0641369915069$$
$$x_{31} = 91.891617631336$$
$$x_{32} = 3.92701410404678$$
$$x_{33} = 10.2101862358417$$
$$x_{34} = -11.7809644712633$$
$$x_{35} = -5.4978396683363$$
$$x_{36} = 68.3296202261614$$
$$x_{37} = 24.3473190031204$$
$$x_{38} = -69.9004501993631$$
$$x_{39} = -27.4889894320297$$
$$x_{40} = -32.2012736277405$$
$$x_{41} = 27.4889680868262$$
$$x_{42} = 11.7810262246701$$
$$x_{43} = 90.320770894749$$
$$x_{44} = 2.35616844993271$$
$$x_{45} = -76.183573738864$$
$$x_{46} = -98.1747238922947$$
$$x_{47} = -96.603943131047$$
$$x_{48} = 62.046440478226$$
$$x_{49} = -41.626132537197$$
$$x_{50} = -10.2101236692732$$
$$x_{51} = 88.7499520940251$$
$$x_{52} = -77.7544170189269$$
$$x_{53} = -25.9181565927284$$
$$x_{54} = -21.2057409948195$$
$$x_{55} = -91.8915951676306$$
$$x_{56} = -19.6349820636656$$
$$x_{57} = -33.7721254392715$$
$$x_{58} = 84.0375912615573$$
$$x_{59} = -11.7809638202413$$
$$x_{60} = 54.1924871034185$$
$$x_{61} = 5.49782609634756$$
$$x_{62} = 60.4756099385565$$
$$x_{63} = 32.2013367887941$$
$$x_{64} = -63.6172829701901$$
$$x_{65} = 16.4933101490183$$
$$x_{66} = 69.900466872915$$
$$x_{67} = 8.63933453425596$$
$$x_{68} = 98.1747864821732$$
$$x_{69} = -85.6084333621604$$