Hallemos los puntos de flexiones, para eso hay que resolver la ecuación
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0$$
(la segunda derivada es igual a cero),
las raíces de la ecuación obtenida serán los puntos de flexión para el gráfico de la función indicado:
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = $$
segunda derivada$$2 \left(x \left(x^{2} - 1\right) \left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} + 3 x \tan{\left(x \right)} + \left(3 x^{2} - 1\right) \left(\tan^{2}{\left(x \right)} + 1\right)\right) = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -81.6446937555336$$
$$x_{2} = -72.2151308721608$$
$$x_{3} = 18.6914180658702$$
$$x_{4} = -59.6400337867216$$
$$x_{5} = -40.7673505273091$$
$$x_{6} = -43.914169748432$$
$$x_{7} = -84.7876453360242$$
$$x_{8} = 37.6196641250491$$
$$x_{9} = 2.27639684529328$$
$$x_{10} = -25.013809217733$$
$$x_{11} = 34.4708756385137$$
$$x_{12} = -78.5016335791697$$
$$x_{13} = -18.6914180658702$$
$$x_{14} = 91.073267590934$$
$$x_{15} = 100.50113024604$$
$$x_{16} = 9.11399178681792$$
$$x_{17} = 21.8553751585661$$
$$x_{18} = -94.2159569713689$$
$$x_{19} = 53.3509485725081$$
$$x_{20} = 97.3585756490797$$
$$x_{21} = -37.6196641250491$$
$$x_{22} = -91.073267590934$$
$$x_{23} = 59.6400337867216$$
$$x_{24} = 25.013809217733$$
$$x_{25} = -12.3309587290799$$
$$x_{26} = 84.7876453360242$$
$$x_{27} = -5.82819309906884$$
$$x_{28} = 78.5016335791697$$
$$x_{29} = -56.4956547093161$$
$$x_{30} = 40.7673505273091$$
$$x_{31} = 47.0602944247052$$
$$x_{32} = 75.3584512533474$$
$$x_{33} = 50.2058542581421$$
$$x_{34} = 15.5187142563086$$
$$x_{35} = -97.3585756490797$$
$$x_{36} = -53.3509485725081$$
$$x_{37} = -31.3206571098888$$
$$x_{38} = 81.6446937555336$$
$$x_{39} = -47.0602944247052$$
$$x_{40} = -75.3584512533474$$
$$x_{41} = -28.1685365194601$$
$$x_{42} = -100.50113024604$$
$$x_{43} = 69.0716536441652$$
$$x_{44} = 56.4956547093161$$
$$x_{45} = -34.4708756385137$$
$$x_{46} = 94.2159569713689$$
$$x_{47} = 0.45901672478924$$
$$x_{48} = 72.2151308721608$$
$$x_{49} = 28.1685365194601$$
$$x_{50} = -65.9279972073077$$
$$x_{51} = -9.11399178681792$$
$$x_{52} = -87.9304999411323$$
$$x_{53} = -21.8553751585661$$
$$x_{54} = -2.27639684529328$$
$$x_{55} = -69.0716536441652$$
$$x_{56} = -62.7841347390722$$
$$x_{57} = -15.5187142563086$$
$$x_{58} = 12.3309587290799$$
$$x_{59} = 62.7841347390722$$
$$x_{60} = 43.914169748432$$
$$x_{61} = 87.9304999411323$$
$$x_{62} = 31.3206571098888$$
$$x_{63} = 5.82819309906884$$
$$x_{64} = 65.9279972073077$$
$$x_{65} = -50.2058542581421$$
Intervalos de convexidad y concavidad:Hallemos los intervales donde la función es convexa o cóncava, para eso veamos cómo se comporta la función en los puntos de flexiones:
Cóncava en los intervalos
$$\left[100.50113024604, \infty\right)$$
Convexa en los intervalos
$$\left[-2.27639684529328, 0.45901672478924\right]$$