El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\sqrt{\cos^{2}{\left(2 x \right)}} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = \frac{\pi}{4}$$
$$x_{2} = \frac{3 \pi}{4}$$
Solución numérica$$x_{1} = 16.4933614313464$$
$$x_{2} = 99.7455667514759$$
$$x_{3} = -54.1924732744239$$
$$x_{4} = 69.9004365423729$$
$$x_{5} = 77.7544181763474$$
$$x_{6} = 32.2013246992954$$
$$x_{7} = 33.7721210260903$$
$$x_{8} = -46.3384916404494$$
$$x_{9} = 54.1924732744239$$
$$x_{10} = 46.3384916404494$$
$$x_{11} = 68.329640215578$$
$$x_{12} = -84.037603483527$$
$$x_{13} = -63.6172512351933$$
$$x_{14} = -98.174770424681$$
$$x_{15} = -85.6083998103219$$
$$x_{16} = 2.35619449019234$$
$$x_{17} = -55.7632696012188$$
$$x_{18} = -71.4712328691678$$
$$x_{19} = 11.7809724509617$$
$$x_{20} = 25.9181393921158$$
$$x_{21} = 55.7632696012188$$
$$x_{22} = -24.3473430653209$$
$$x_{23} = 91.8915851175014$$
$$x_{24} = 90.3207887907066$$
$$x_{25} = -90.3207887907066$$
$$x_{26} = -40.0553063332699$$
$$x_{27} = -41.6261026600648$$
$$x_{28} = 98.174770424681$$
$$x_{29} = -5.49778714378214$$
$$x_{30} = -76.1836218495525$$
$$x_{31} = -27.4889357189107$$
$$x_{32} = -62.0464549083984$$
$$x_{33} = -18.0641577581413$$
$$x_{34} = -68.329640215578$$
$$x_{35} = 84.037603483527$$
$$x_{36} = 82.4668071567321$$
$$x_{37} = 60.4756585816035$$
$$x_{38} = -11.7809724509617$$
$$x_{39} = 38.484510006475$$
$$x_{40} = 3.92699081698724$$
$$x_{41} = -19.6349540849362$$
$$x_{42} = 62.0464549083984$$
$$x_{43} = -3535.07713345191$$
$$x_{44} = 76.1836218495525$$
$$x_{45} = -32.2013246992954$$
$$x_{46} = 24.3473430653209$$
$$x_{47} = 10.2101761241668$$
$$x_{48} = -49.4800842940392$$
$$x_{49} = -93.4623814442964$$
$$x_{50} = 47.9092879672443$$
$$x_{51} = -10.2101761241668$$
$$x_{52} = -77.7544181763474$$
$$x_{53} = -99.7455667514759$$
$$x_{54} = -33.7721210260903$$
$$x_{55} = -29.0597320457056$$