El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\frac{81}{125} - \frac{11011 \cos{\left(\frac{2 \pi x}{\frac{11}{5}} \right)}}{1000} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = \frac{11 \left(- \operatorname{acos}{\left(\frac{648}{11011} \right)} + 2 \pi\right)}{10 \pi}$$
$$x_{2} = \frac{11 \operatorname{acos}{\left(\frac{648}{11011} \right)}}{10 \pi}$$
Solución numérica$$x_{1} = 25.8706177875544$$
$$x_{2} = -33.5293822124456$$
$$x_{3} = 13.7293822124456$$
$$x_{4} = 37.9293822124456$$
$$x_{5} = 74.2706177875544$$
$$x_{6} = 52.2706177875544$$
$$x_{7} = 72.0706177875544$$
$$x_{8} = -57.7293822124456$$
$$x_{9} = -50.0706177875544$$
$$x_{10} = 62.1293822124456$$
$$x_{11} = 57.7293822124456$$
$$x_{12} = 35.7293822124456$$
$$x_{13} = -1.67061778755441$$
$$x_{14} = -84.1293822124456$$
$$x_{15} = -70.9293822124456$$
$$x_{16} = 39.0706177875544$$
$$x_{17} = -55.5293822124456$$
$$x_{18} = 81.9293822124456$$
$$x_{19} = 47.8706177875544$$
$$x_{20} = -59.9293822124456$$
$$x_{21} = -89.6706177875544$$
$$x_{22} = -79.7293822124456$$
$$x_{23} = -40.1293822124456$$
$$x_{24} = -87.4706177875544$$
$$x_{25} = 3.87061778755441$$
$$x_{26} = -72.0706177875544$$
$$x_{27} = 66.5293822124456$$
$$x_{28} = 0.529382212445594$$
$$x_{29} = 17.0706177875544$$
$$x_{30} = 91.8706177875544$$
$$x_{31} = 61.0706177875544$$
$$x_{32} = -21.4706177875544$$
$$x_{33} = -67.6706177875544$$
$$x_{34} = 79.7293822124456$$
$$x_{35} = 105.070617787554$$
$$x_{36} = 88.5293822124456$$
$$x_{37} = 22.5293822124456$$
$$x_{38} = 20.3293822124456$$
$$x_{39} = 30.2706177875544$$
$$x_{40} = -52.2706177875544$$
$$x_{41} = 10.4706177875544$$
$$x_{42} = -3.87061778755441$$
$$x_{43} = 96.2706177875544$$
$$x_{44} = 59.9293822124456$$
$$x_{45} = 86.3293822124456$$
$$x_{46} = -48.9293822124456$$
$$x_{47} = 54.4706177875544$$
$$x_{48} = -28.0706177875544$$
$$x_{49} = -94.0706177875544$$
$$x_{50} = -11.5293822124456$$
$$x_{51} = -65.4706177875544$$
$$x_{52} = -99.5293822124456$$
$$x_{53} = 28.0706177875544$$
$$x_{54} = 44.5293822124456$$
$$x_{55} = -15.9293822124456$$
$$x_{56} = -13.7293822124456$$
$$x_{57} = -8.27061778755441$$
$$x_{58} = -30.2706177875544$$
$$x_{59} = -18.1293822124456$$
$$x_{60} = 84.1293822124456$$
$$x_{61} = -96.2706177875544$$
$$x_{62} = 98.4706177875544$$
$$x_{63} = -92.9293822124456$$
$$x_{64} = 42.3293822124456$$
$$x_{65} = 18.1293822124456$$
$$x_{66} = 64.3293822124456$$
$$x_{67} = 76.4706177875544$$
$$x_{68} = -47.8706177875544$$
$$x_{69} = -81.9293822124456$$
$$x_{70} = -37.9293822124456$$
$$x_{71} = 69.8706177875544$$
$$x_{72} = 40.1293822124456$$
$$x_{73} = -35.7293822124456$$
$$x_{74} = -74.2706177875544$$
$$x_{75} = -69.8706177875544$$
$$x_{76} = 6.07061778755441$$
$$x_{77} = 94.0706177875544$$
$$x_{78} = -23.6706177875544$$
$$x_{79} = -26.9293822124456$$
$$x_{80} = -45.6706177875544$$
$$x_{81} = 50.0706177875544$$
$$x_{82} = -43.4706177875544$$
$$x_{83} = 8.27061778755441$$
$$x_{84} = -4.92938221244559$$
$$x_{85} = 15.9293822124456$$
$$x_{86} = 32.4706177875544$$
$$x_{87} = -62.1293822124456$$
$$x_{88} = 83.0706177875544$$
$$x_{89} = -6.07061778755441$$
$$x_{90} = -25.8706177875544$$
$$x_{91} = -77.5293822124456$$
$$x_{92} = -91.8706177875544$$