El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$- \log{\left(\cos{\left(x \right)} \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = 0$$
$$x_{2} = 2 \pi$$
Solución numérica$$x_{1} = 31.4159255531763$$
$$x_{2} = 87.9645942296464$$
$$x_{3} = -43.9822971932261$$
$$x_{4} = -12.5663702522378$$
$$x_{5} = -37.6991118773736$$
$$x_{6} = -87.9645943355219$$
$$x_{7} = -56.5486688343165$$
$$x_{8} = -18.8495562408585$$
$$x_{9} = -62.8318534517187$$
$$x_{10} = -75.3982238864105$$
$$x_{11} = 50.2654824640562$$
$$x_{12} = -50.2654827822791$$
$$x_{13} = 18.8495567580196$$
$$x_{14} = -75.3982234018825$$
$$x_{15} = 69.1150390932802$$
$$x_{16} = 6.28318528416623$$
$$x_{17} = 62.8318538684035$$
$$x_{18} = 25.1327409700176$$
$$x_{19} = 62.831852735923$$
$$x_{20} = 94.2477796068599$$
$$x_{21} = 31.4159269101267$$
$$x_{22} = -62.8318528736237$$
$$x_{23} = -62.8318536803612$$
$$x_{24} = 37.6991120433529$$
$$x_{25} = -69.1150374752626$$
$$x_{26} = 43.9822971695019$$
$$x_{27} = -12.5663716213936$$
$$x_{28} = 18.8495570029843$$
$$x_{29} = -100.530965897751$$
$$x_{30} = 50.2654824463311$$
$$x_{31} = 37.6991114441887$$
$$x_{32} = 87.9645943360512$$
$$x_{33} = 100.530965106382$$
$$x_{34} = -43.9822971744998$$
$$x_{35} = 0$$
$$x_{36} = -56.5486674143785$$
$$x_{37} = -18.8495553258088$$
$$x_{38} = 25.1327406563971$$
$$x_{39} = -6.28318566745615$$
$$x_{40} = -50.2654822771894$$
$$x_{41} = 25.1327418431203$$
$$x_{42} = -31.4159262776781$$
$$x_{43} = 100.530964753022$$
$$x_{44} = -69.1150373853363$$
$$x_{45} = 94.2477796093522$$
$$x_{46} = -56.5486687640637$$
$$x_{47} = 43.982297089421$$
$$x_{48} = -87.9645943584596$$
$$x_{49} = -25.1327403562086$$
$$x_{50} = 69.1150381807919$$
$$x_{51} = -25.1327415878584$$
$$x_{52} = 56.5486675932357$$
$$x_{53} = 81.681409203672$$
$$x_{54} = 75.3982227418079$$
$$x_{55} = 31.4159255304025$$
$$x_{56} = 12.5663704334084$$
$$x_{57} = -25.1327401930409$$
$$x_{58} = 62.8318542034359$$
$$x_{59} = -100.53096457631$$
$$x_{60} = -37.6991118203008$$
$$x_{61} = 69.1150390127643$$
$$x_{62} = -69.1150387500801$$
$$x_{63} = -6.28318511692891$$
$$x_{64} = -18.8495565116576$$
$$x_{65} = 75.3982226911418$$
$$x_{66} = 18.8495555741382$$
$$x_{67} = 25.1327418930934$$
$$x_{68} = -18.8495557286473$$
$$x_{69} = 6.28318532165763$$
$$x_{70} = -31.4159267264704$$
$$x_{71} = -94.2477794374461$$
$$x_{72} = -12.5663716386669$$
$$x_{73} = 75.39822407273$$
$$x_{74} = -94.2477799001796$$
$$x_{75} = 12.5663708485373$$
$$x_{76} = 81.6814085526449$$
$$x_{77} = -81.6814089617871$$
$$x_{78} = 56.5486679766099$$
$$x_{79} = -62.8318524940769$$
$$x_{80} = 69.1150378238503$$
$$x_{81} = -81.6814090384469$$