El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$7 \tan^{2}{\left(x \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = 0$$
Solución numérica$$x_{1} = 6.28318528408307$$
$$x_{2} = -28.274333676669$$
$$x_{3} = 94.2477796093519$$
$$x_{4} = -21.9911485864129$$
$$x_{5} = -94.2477794213743$$
$$x_{6} = 0$$
$$x_{7} = -75.3982239115218$$
$$x_{8} = 78.53981615825$$
$$x_{9} = 100.530964739312$$
$$x_{10} = 72.2566310277136$$
$$x_{11} = -31.4159267482748$$
$$x_{12} = -72.2566308398808$$
$$x_{13} = -43.9822971744223$$
$$x_{14} = -50.265482258314$$
$$x_{15} = 12.5663704145927$$
$$x_{16} = 50.2654824463153$$
$$x_{17} = 37.6991120687848$$
$$x_{18} = -87.9645943581507$$
$$x_{19} = -65.973445764663$$
$$x_{20} = 59.6902602145004$$
$$x_{21} = -97.3893724932976$$
$$x_{22} = -37.6991118775909$$
$$x_{23} = -6.28318509494079$$
$$x_{24} = 28.2743338651162$$
$$x_{25} = 56.5486675771117$$
$$x_{26} = 43.9822971695754$$
$$x_{27} = -15.7079632968116$$
$$x_{28} = 87.9645943363399$$
$$x_{29} = 59.690260650792$$
$$x_{30} = -59.6902604582742$$
$$x_{31} = -9.42477816679559$$
$$x_{32} = 34.5575189958939$$
$$x_{33} = 21.9911485852339$$
$$x_{34} = 65.9734457532278$$
$$x_{35} = -53.4070753298489$$
$$x_{36} = 15.7079634868755$$
$$x_{37} = -81.6814090388783$$
$$x_{38} = 81.681409232902$$