El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\tan{\left(3 x \right)} + \frac{2}{5} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = - \frac{\operatorname{atan}{\left(\frac{2}{5} \right)}}{3}$$
Solución numérica$$x_{1} = 65.8466102663482$$
$$x_{2} = -13.7404036245932$$
$$x_{3} = 98.3097343534427$$
$$x_{4} = 12.4395351553217$$
$$x_{5} = 100.404129455836$$
$$x_{6} = 8.25074495053533$$
$$x_{7} = -92.2802199643381$$
$$x_{8} = 89.9321539438699$$
$$x_{9} = 59.5634249591686$$
$$x_{10} = 41.7610665888265$$
$$x_{11} = 54.3274372031856$$
$$x_{12} = -33.6371570973286$$
$$x_{13} = 19.7699180136979$$
$$x_{14} = 50.1386469983992$$
$$x_{15} = 36.5250788328435$$
$$x_{16} = 74.224190675921$$
$$x_{17} = -83.9026395547653$$
$$x_{18} = 52.2330421007924$$
$$x_{19} = -77.6194542475857$$
$$x_{20} = -94.3746150667313$$
$$x_{21} = -6.41002076621704$$
$$x_{22} = -81.8082444523721$$
$$x_{23} = -90.1858248619449$$
$$x_{24} = -85.9970346571585$$
$$x_{25} = -22.117984034166$$
$$x_{26} = 17.6755229113047$$
$$x_{27} = 58.516227407972$$
$$x_{28} = -46.2035277116878$$
$$x_{29} = -26.3067742389524$$
$$x_{30} = -24.2123791365592$$
$$x_{31} = 34.4306837304503$$
$$x_{32} = -2.22123056143065$$
$$x_{33} = -39.9203424045082$$
$$x_{34} = -66.1002811844231$$
$$x_{35} = -55.6283056724571$$
$$x_{36} = -68.1946762868163$$
$$x_{37} = -74.4778615939959$$
$$x_{38} = 14.5339302577149$$
$$x_{39} = -37.825947302115$$
$$x_{40} = 67.9410053687414$$
$$x_{41} = 45.9498567936128$$
$$x_{42} = 61.6578200615618$$
$$x_{43} = 76.3185857783142$$
$$x_{44} = -42.0147375069014$$
$$x_{45} = 92.0265490462631$$
$$x_{46} = -50.3923179164741$$
$$x_{47} = 43.8554616912197$$
$$x_{48} = -72.3834664916027$$
$$x_{49} = 26.0531033208775$$
$$x_{50} = -17.9291938293796$$
$$x_{51} = -57.7227007748503$$
$$x_{52} = 94.1209441486563$$
$$x_{53} = -99.6106028227142$$
$$x_{54} = 6.15634984814213$$
$$x_{55} = -88.0914297595517$$
$$x_{56} = -31.5427619949354$$
$$x_{57} = -7.45721831741364$$
$$x_{58} = -29.4483668925422$$
$$x_{59} = -70.2890713892095$$
$$x_{60} = -44.1091326092946$$
$$x_{61} = 32.3362886280571$$
$$x_{62} = 81.5545735342972$$
$$x_{63} = 30.2418935256639$$
$$x_{64} = 4.06195474574894$$
$$x_{65} = -15.8347987269864$$
$$x_{66} = 87.8377588414768$$
$$x_{67} = 10.3451400529285$$
$$x_{68} = 56.4218323055788$$
$$x_{69} = 72.1297955735278$$
$$x_{70} = 80.5073759831006$$
$$x_{71} = 28.1474984232707$$
$$x_{72} = -0.126835459037455$$
$$x_{73} = -11.6460085222$$
$$x_{74} = 23.9587082184843$$
$$x_{75} = 1.96755964335574$$
$$x_{76} = -4.31562566382385$$
$$x_{77} = -35.7315521997218$$
$$x_{78} = -75.5250591451925$$
$$x_{79} = -97.516207720321$$
$$x_{80} = 39.6666714864333$$
$$x_{81} = -61.9114909796367$$
$$x_{82} = -64.0058860820299$$
$$x_{83} = -20.0235889317728$$
$$x_{84} = 83.6489686366904$$
$$x_{85} = 63.752215163955$$
$$x_{86} = 70.0354004711346$$
$$x_{87} = 78.4129808807074$$
$$x_{88} = -59.8170958772435$$
$$x_{89} = -53.5339105700639$$
$$x_{90} = 85.7433637390836$$
$$x_{91} = -28.4011693413456$$
$$x_{92} = 48.044251896006$$
$$x_{93} = -9.55161341980683$$
$$x_{94} = 21.8643131160911$$
$$x_{95} = -48.2979228140809$$
$$x_{96} = 37.5722763840401$$
$$x_{97} = 15.5811278089115$$
$$x_{98} = -79.7138493499789$$
$$x_{99} = 96.2153392510495$$
$$x_{100} = -52.4867130188673$$
$$x_{101} = -96.4690101691244$$