El gráfico de la función cruce el eje T con f = 0
o sea hay que resolver la ecuación:
$$\frac{\cos{\left(t \right)}}{3} - \frac{\cos{\left(2 t \right)}}{3} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje T:
Solución analítica$$t_{1} = 0$$
$$t_{2} = - \frac{4 \pi}{3}$$
$$t_{3} = - \frac{2 \pi}{3}$$
$$t_{4} = \frac{2 \pi}{3}$$
$$t_{5} = \frac{4 \pi}{3}$$
$$t_{6} = 2 \pi$$
Solución numérica$$t_{1} = 90.0589894029074$$
$$t_{2} = 50.2654824463501$$
$$t_{3} = -33.5103216382911$$
$$t_{4} = -90.0589894029074$$
$$t_{5} = -18.8495558006412$$
$$t_{6} = -73.3038285837618$$
$$t_{7} = -43.9822971745925$$
$$t_{8} = -85.870199198121$$
$$t_{9} = 56.5486676119735$$
$$t_{10} = -29.3215314335047$$
$$t_{11} = 79.5870138909414$$
$$t_{12} = -37.6991118771132$$
$$t_{13} = -83.7758040957278$$
$$t_{14} = 92.1533845053006$$
$$t_{15} = 48.1710873550435$$
$$t_{16} = 81.6814091712551$$
$$t_{17} = -6.28318514161788$$
$$t_{18} = 69.1150383780256$$
$$t_{19} = 54.4542726622231$$
$$t_{20} = -79.5870138909414$$
$$t_{21} = -18.8495558711096$$
$$t_{22} = 37.6991120149696$$
$$t_{23} = -87.9645943588266$$
$$t_{24} = 62.8318528532238$$
$$t_{25} = 46.0766922526503$$
$$t_{26} = 33.5103216382911$$
$$t_{27} = -69.1150385967809$$
$$t_{28} = 0$$
$$t_{29} = -52.3598775598299$$
$$t_{30} = -92.1533845053006$$
$$t_{31} = 25.1327411125589$$
$$t_{32} = 85.870199198121$$
$$t_{33} = 60.7374579694027$$
$$t_{34} = 77.4926187885482$$
$$t_{35} = 41.8879020478639$$
$$t_{36} = -18.8495558410301$$
$$t_{37} = -62.8318529503654$$
$$t_{38} = 81.6814099884351$$
$$t_{39} = -56.5486675394273$$
$$t_{40} = 31.4159267619367$$
$$t_{41} = -41.8879020478639$$
$$t_{42} = 94.2477796093525$$
$$t_{43} = 12.5663704551863$$
$$t_{44} = 25.1327412731354$$
$$t_{45} = 69.1150383295746$$
$$t_{46} = 69.115037832119$$
$$t_{47} = 4.18879020478639$$
$$t_{48} = -10.471975511966$$
$$t_{49} = 14.6607657167524$$
$$t_{50} = 43.9822969706241$$
$$t_{51} = 39.7935069454707$$
$$t_{52} = 6.28318528426584$$
$$t_{53} = -62.8318537995483$$
$$t_{54} = -27.2271363311115$$
$$t_{55} = -96.342174710087$$
$$t_{56} = 10.471975511966$$
$$t_{57} = -69.11503909537$$
$$t_{58} = -54.4542726622231$$
$$t_{59} = 58.6430628670095$$
$$t_{60} = 18.8495557025416$$
$$t_{61} = 100.530964769014$$
$$t_{62} = -62.8318529623378$$
$$t_{63} = -39.7935069454707$$
$$t_{64} = 83.7758040957278$$
$$t_{65} = 35.6047167406843$$
$$t_{66} = -12.5663703884691$$
$$t_{67} = 25.13274122338$$
$$t_{68} = -81.6814090379303$$
$$t_{69} = 87.9645943357073$$
$$t_{70} = -4.18879020478639$$
$$t_{71} = 25.1327417460082$$
$$t_{72} = -50.2654822985064$$
$$t_{73} = -71.2094334813686$$
$$t_{74} = 96.342174710087$$
$$t_{75} = 43.9822971694142$$
$$t_{76} = 52.3598775598299$$
$$t_{77} = -94.2477794556977$$
$$t_{78} = 69.1150384283402$$
$$t_{79} = -48.1710873550435$$
$$t_{80} = 12.5663700882745$$
$$t_{81} = -75.3982238575994$$
$$t_{82} = -46.0766922526503$$
$$t_{83} = -35.6047167406843$$
$$t_{84} = 75.3982239117447$$
$$t_{85} = -8.37758040957278$$
$$t_{86} = -77.4926187885482$$
$$t_{87} = -98.4365698124802$$
$$t_{88} = -25.1327414474833$$
$$t_{89} = -18.8495555012277$$
$$t_{90} = -2.0943951023932$$
$$t_{91} = 16.7551608191456$$
$$t_{92} = -31.4159267013407$$
$$t_{93} = 98.4365698124802$$
$$t_{94} = 2.0943951023932$$
$$t_{95} = -100.530964690899$$
$$t_{96} = 8.37758040957278$$