El gráfico de la función cruce el eje Y con f = 0
o sea hay que resolver la ecuación:
$$2 \left(\cos{\left(y \right)} + 1\right) = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje Y:
Solución analítica$$y_{1} = \pi$$
Solución numérica$$y_{1} = 3.1415922548952$$
$$y_{2} = 47.1238902162437$$
$$y_{3} = 28.2743335663982$$
$$y_{4} = -21.9911485864417$$
$$y_{5} = -21.991148226056$$
$$y_{6} = 21.9911485852059$$
$$y_{7} = -3.14159295109225$$
$$y_{8} = 72.2566310277176$$
$$y_{9} = 59.6902599104079$$
$$y_{10} = -28.2743340989896$$
$$y_{11} = 21.9911480932338$$
$$y_{12} = -84.8230020565447$$
$$y_{13} = 65.9734457529812$$
$$y_{14} = 40.8407049800347$$
$$y_{15} = -47.1238901083229$$
$$y_{16} = 15.7079634518075$$
$$y_{17} = 65.9734460390947$$
$$y_{18} = 15.7079627593774$$
$$y_{19} = -53.4070745963886$$
$$y_{20} = -84.8230012511693$$
$$y_{21} = 28.2743338651796$$
$$y_{22} = 40.8407045792514$$
$$y_{23} = 97.3893717959212$$
$$y_{24} = -97.3893716284562$$
$$y_{25} = -72.2566315419804$$
$$y_{26} = -72.2566308657983$$
$$y_{27} = -40.8407049008781$$
$$y_{28} = 59.6902606104322$$
$$y_{29} = 47.123889410773$$
$$y_{30} = -9.42477752082051$$
$$y_{31} = -21.9911490521325$$
$$y_{32} = -34.5575188899093$$
$$y_{33} = 78.5398168562347$$
$$y_{34} = -47.1238893275319$$
$$y_{35} = 91.1061865667532$$
$$y_{36} = 34.5575197055812$$
$$y_{37} = 84.8230021335997$$
$$y_{38} = 40.8407045848602$$
$$y_{39} = -65.9734449870253$$
$$y_{40} = -28.2743343914215$$
$$y_{41} = -97.3893717476911$$
$$y_{42} = 78.5398152766482$$
$$y_{43} = -91.106187265474$$
$$y_{44} = -15.7079632965989$$
$$y_{45} = 84.8230013636028$$
$$y_{46} = 9.42477748794163$$
$$y_{47} = 15.707963957033$$
$$y_{48} = -15.7079635641079$$
$$y_{49} = -15.707962774825$$
$$y_{50} = -1127.83176318906$$
$$y_{51} = -53.407075294995$$
$$y_{52} = 59.6902600526626$$
$$y_{53} = -91.1061864815274$$
$$y_{54} = -65.9734457649277$$
$$y_{55} = -53.4070745786761$$
$$y_{56} = 65.9734452390837$$
$$y_{57} = 97.389372581711$$
$$y_{58} = -59.6902604578012$$
$$y_{59} = 28.2743343711514$$
$$y_{60} = 53.4070746418597$$
$$y_{61} = -34.5575196658297$$
$$y_{62} = -3.14159217367683$$
$$y_{63} = 34.5575190219169$$
$$y_{64} = -65.9734461969855$$
$$y_{65} = -78.5398168194507$$
$$y_{66} = 78.5398161804942$$
$$y_{67} = -65.9734453607004$$
$$y_{68} = -59.6902599212271$$
$$y_{69} = 21.9911489072506$$
$$y_{70} = 91.1061873718352$$
$$y_{71} = -28.2743337069329$$
$$y_{72} = -40.8407049290801$$
$$y_{73} = 40.8407042062167$$
$$y_{74} = 72.2566306985$$
$$y_{75} = 9.42477826738203$$
$$y_{76} = 15.7079629803241$$
$$y_{77} = -9.4247781365785$$
$$y_{78} = 72.2566315166773$$
$$y_{79} = -9.42477744529557$$
$$y_{80} = -97.3893724533348$$
$$y_{81} = 78.5398166181283$$
$$y_{82} = -40.8407040952604$$
$$y_{83} = -72.2566311847166$$
$$y_{84} = -59.6902606928653$$
$$y_{85} = 53.407075424589$$
$$y_{86} = 3.14159306054457$$
$$y_{87} = -78.5398160472843$$
$$y_{88} = 34.5575195449229$$