Graph of the function intersects the axis X at f = 0
so we need to solve the equation:
$$\cos{\left(x \right)} + 1 = 0$$
Solve this equationThe points of intersection with the axis X:
Analytical solution$$x_{1} = \pi$$
Numerical solution$$x_{1} = -78.5398168194507$$
$$x_{2} = -21.9911490521325$$
$$x_{3} = -9.42477752082051$$
$$x_{4} = 59.6902606104322$$
$$x_{5} = 40.8407045792514$$
$$x_{6} = 91.1061865667532$$
$$x_{7} = 65.9734452390837$$
$$x_{8} = 15.7079627593774$$
$$x_{9} = 9.42477748794163$$
$$x_{10} = -59.6902604578012$$
$$x_{11} = -28.2743337069329$$
$$x_{12} = 78.5398166181283$$
$$x_{13} = -65.9734449870253$$
$$x_{14} = -15.707962774825$$
$$x_{15} = 91.1061873718352$$
$$x_{16} = -15.7079632965989$$
$$x_{17} = 65.9734460390947$$
$$x_{18} = 97.3893717959212$$
$$x_{19} = 28.2743338651796$$
$$x_{20} = -72.2566311847166$$
$$x_{21} = -40.8407049008781$$
$$x_{22} = 34.5575197055812$$
$$x_{23} = -34.5575196658297$$
$$x_{24} = -47.1238901083229$$
$$x_{25} = -9.4247781365785$$
$$x_{26} = 78.5398168562347$$
$$x_{27} = 78.5398152766482$$
$$x_{28} = -21.9911485864417$$
$$x_{29} = 84.8230013636028$$
$$x_{30} = -1127.83176318906$$
$$x_{31} = 47.1238902162437$$
$$x_{32} = -47.1238893275319$$
$$x_{33} = -3.14159217367683$$
$$x_{34} = 72.2566315166773$$
$$x_{35} = 78.5398149750205$$
$$x_{36} = -53.4070745963886$$
$$x_{37} = 34.5575195449229$$
$$x_{38} = -84.8230012511693$$
$$x_{39} = 21.9911489072506$$
$$x_{40} = 47.123889410773$$
$$x_{41} = 15.7079629803241$$
$$x_{42} = 3.1415922548952$$
$$x_{43} = 9.42477826738203$$
$$x_{44} = -65.9734461969855$$
$$x_{45} = 28.2743343711514$$
$$x_{46} = 3.14159306054457$$
$$x_{47} = -28.2743343914215$$
$$x_{48} = 72.2566310277176$$
$$x_{49} = -91.1061864815274$$
$$x_{50} = -65.9734457649277$$
$$x_{51} = -28.2743340989896$$
$$x_{52} = -78.5398160472843$$
$$x_{53} = 53.407075424589$$
$$x_{54} = -72.2566315419804$$
$$x_{55} = 65.9734457529812$$
$$x_{56} = 72.2566306985$$
$$x_{57} = -72.2566308657983$$
$$x_{58} = 28.2743335663982$$
$$x_{59} = -3.14159295109225$$
$$x_{60} = 21.9911480932338$$
$$x_{61} = 21.9911485852059$$
$$x_{62} = 53.4070746418597$$
$$x_{63} = 40.8407049800347$$
$$x_{64} = -34.5575188899093$$
$$x_{65} = -59.6902599212271$$
$$x_{66} = -59.6902606928653$$
$$x_{67} = 78.5398161804942$$
$$x_{68} = -53.407075294995$$
$$x_{69} = 59.6902599104079$$
$$x_{70} = -40.8407049290801$$
$$x_{71} = -91.106187265474$$
$$x_{72} = -15.7079635641079$$
$$x_{73} = -21.991148226056$$
$$x_{74} = 15.707963957033$$
$$x_{75} = -97.3893717476911$$
$$x_{76} = 34.5575190219169$$
$$x_{77} = -97.3893716284562$$
$$x_{78} = 40.8407045848602$$
$$x_{79} = -40.8407040952604$$
$$x_{80} = -9.42477744529557$$
$$x_{81} = 59.6902600526626$$
$$x_{82} = 40.8407042062167$$
$$x_{83} = -84.8230020565447$$
$$x_{84} = 53.4070766553897$$
$$x_{85} = -97.3893724533348$$
$$x_{86} = -65.9734453607004$$
$$x_{87} = -53.4070745786761$$
$$x_{88} = 15.7079634518075$$
$$x_{89} = 97.389372581711$$
$$x_{90} = 84.8230021335997$$