Graph of the function intersects the axis X at f = 0
so we need to solve the equation:
$$\cos{\left(\frac{x}{2} \right)} + 1 = 0$$
Solve this equationThe points of intersection with the axis X:
Analytical solution$$x_{1} = 2 \pi$$
Numerical solution$$x_{1} = 31.4159255107699$$
$$x_{2} = -18.8495543136467$$
$$x_{3} = -81.6814098544517$$
$$x_{4} = -18.8495554800568$$
$$x_{5} = 56.548668769019$$
$$x_{6} = 973.893720162307$$
$$x_{7} = -420.973417050673$$
$$x_{8} = -6.28318627375063$$
$$x_{9} = 69.1150394039813$$
$$x_{10} = -6.28318500560576$$
$$x_{11} = -31.4159274639505$$
$$x_{12} = -94.2477790629797$$
$$x_{13} = 43.9822963919738$$
$$x_{14} = 18.8495549415754$$
$$x_{15} = 69.115037955532$$
$$x_{16} = 6.28318445599649$$
$$x_{17} = 56.5486675992574$$
$$x_{18} = -69.1150393645777$$
$$x_{19} = 56.5486681672153$$
$$x_{20} = -56.5486677946696$$
$$x_{21} = 31.4159275256971$$
$$x_{22} = 43.9822980146158$$
$$x_{23} = -31.4159267183799$$
$$x_{24} = -69.1150405916551$$
$$x_{25} = -31.4159258676764$$
$$x_{26} = 18.8495569537229$$
$$x_{27} = -18.8495563601837$$
$$x_{28} = -31.4159269573538$$
$$x_{29} = -69.115038701061$$
$$x_{30} = -69.1150378269834$$
$$x_{31} = 81.6814079898679$$
$$x_{32} = 56.5486684458067$$
$$x_{33} = -18.8495548993085$$
$$x_{34} = 69.1150368714384$$
$$x_{35} = -6.28318597231491$$
$$x_{36} = 6.28318624191326$$
$$x_{37} = 56.5486668446775$$
$$x_{38} = -6.28318512498487$$
$$x_{39} = 81.681409932803$$
$$x_{40} = 56.5486672894687$$
$$x_{41} = 94.2477803922665$$
$$x_{42} = 94.2477805288104$$
$$x_{43} = 6.28318528419795$$
$$x_{44} = -56.5486687887842$$
$$x_{45} = 81.6814094388795$$
$$x_{46} = -81.68140804614$$
$$x_{47} = -81.6814090382823$$
$$x_{48} = 43.9822979229286$$
$$x_{49} = -69.115037346238$$
$$x_{50} = 31.415926404003$$
$$x_{51} = 43.9822962232996$$
$$x_{52} = -6.28318630492991$$
$$x_{53} = -43.9822963521153$$
$$x_{54} = -56.5486667805662$$
$$x_{55} = -6.28318437561383$$
$$x_{56} = 31.4159259869291$$
$$x_{57} = 18.8495561010751$$
$$x_{58} = 6.28318608026041$$
$$x_{59} = 81.6814083413212$$
$$x_{60} = -94.2477794433785$$
$$x_{61} = -94.2477802857943$$
$$x_{62} = 43.982297169474$$
$$x_{63} = -31.4159267991785$$
$$x_{64} = 94.2477796093523$$
$$x_{65} = 69.1150397628024$$
$$x_{66} = -56.5486683277755$$
$$x_{67} = -56.548667456373$$
$$x_{68} = 81.6814091930517$$
$$x_{69} = -18.8495572113627$$
$$x_{70} = -6.28318480992034$$
$$x_{71} = 94.2477787666659$$
$$x_{72} = -18.8495569383691$$
$$x_{73} = -81.6814097251289$$
$$x_{74} = -31.4159255258029$$
$$x_{75} = 69.1150373651011$$
$$x_{76} = 18.8495554920234$$
$$x_{77} = -94.2477786842917$$
$$x_{78} = -43.9822979202134$$
$$x_{79} = 6.28318454684724$$
$$x_{80} = 18.8495564877336$$
$$x_{81} = 18.8495556154405$$
$$x_{82} = -43.9822971745293$$
$$x_{83} = 31.4159268602638$$
$$x_{84} = -43.9822980632848$$
$$x_{85} = -81.6814082319334$$
$$x_{86} = 69.115038835587$$
$$x_{87} = -43.982296295854$$
$$x_{88} = -94.2477805989545$$
$$x_{89} = 81.6814069775521$$
$$x_{90} = -69.1150380827831$$
$$x_{91} = 94.2477788210844$$