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$$2 \left(4 x^{2} \left(\tan^{2}{\left(x^{2} \right)} + 1\right) \tan{\left(x^{2} \right)} + \tan^{2}{\left(x^{2} \right)} + 1\right) = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -45.084479855911$$
$$x_{2} = 70.2974053113422$$
$$x_{3} = -15.7538824522744$$
$$x_{4} = 98.0152554894128$$
$$x_{5} = -23.9773021993105$$
$$x_{6} = -58.0055657475439$$
$$x_{7} = 67.9337880141555$$
$$x_{8} = -38.2620177957948$$
$$x_{9} = -65.7482428168775$$
$$x_{10} = -21.9955620959205$$
$$x_{11} = -53.9944246823664$$
$$x_{12} = 30.2357931718758$$
$$x_{13} = -3.96131707443208$$
$$x_{14} = 10.0263890839373$$
$$x_{15} = 21.9955620959205$$
$$x_{16} = -59.9760245336446$$
$$x_{17} = 46.2539131343586$$
$$x_{18} = -19.7371945141746$$
$$x_{19} = 100.374735941116$$
$$x_{20} = -9.70799294173983$$
$$x_{21} = 84.0001015745334$$
$$x_{22} = -51.9785493213814$$
$$x_{23} = 36.2379019649839$$
$$x_{24} = 26.1699605167475$$
$$x_{25} = -77.7458952237758$$
$$x_{26} = 66.2480556703503$$
$$x_{27} = 24.2379330940786$$
$$x_{28} = 93.7894418451826$$
$$x_{29} = 28.2482604900649$$
$$x_{30} = 18.2485087212107$$
$$x_{31} = 42.2424488771403$$
$$x_{32} = -25.6852891421007$$
$$x_{33} = 90.1166853515224$$
$$x_{34} = -49.5019410506056$$
$$x_{35} = 64.249923628404$$
$$x_{36} = -93.6721316773806$$
$$x_{37} = 3.96131707443208$$
$$x_{38} = 8.1221706533684$$
$$x_{39} = -11.757051848034$$
$$x_{40} = -97.9992281397806$$
$$x_{41} = 43.812246930533$$
$$x_{42} = 88.249692102287$$
$$x_{43} = 50.0384776453561$$
$$x_{44} = -5.87794891821309$$
$$x_{45} = -105.412585554328$$
$$x_{46} = -89.7498943329059$$
$$x_{47} = 56.2736644965707$$
$$x_{48} = -41.7562423999034$$
$$x_{49} = 34.001557027258$$
$$x_{50} = 62.0105583185608$$
$$x_{51} = -47.9218543142169$$
$$x_{52} = -27.7432852294635$$
$$x_{53} = -87.9108519779118$$
$$x_{54} = 86.2148953763774$$
$$x_{55} = -56.0779294085062$$
$$x_{56} = 6.39019423112011$$
$$x_{57} = -95.7453253997488$$
$$x_{58} = -81.3399907221167$$
$$x_{59} = 32.2956424506555$$
$$x_{60} = 72.0192295354316$$
$$x_{61} = 58.2218034714853$$
$$x_{62} = 54.255619353996$$
$$x_{63} = 78.2493708665866$$
$$x_{64} = 1.74930740111531$$
$$x_{65} = 11.757051848034$$
$$x_{66} = 92.1335081311262$$
$$x_{67} = 48.2485238004028$$
$$x_{68} = -17.7245160605986$$
$$x_{69} = -75.9884679014017$$
$$x_{70} = -31.7066144592746$$
$$x_{71} = -29.764556877646$$
$$x_{72} = -85.9959828872556$$
$$x_{73} = -84.0001015745334$$
$$x_{74} = 14.1795869624156$$
$$x_{75} = 40.1060504564238$$
$$x_{76} = -34.001557027258$$
$$x_{77} = -73.8711472326801$$
$$x_{78} = -35.7579084188236$$
$$x_{79} = 76.2567240235449$$
$$x_{80} = -39.7519929884018$$
$$x_{81} = -67.8180771660422$$
$$x_{82} = 52.2498222427207$$
$$x_{83} = 16.2447787164853$$
$$x_{84} = -45.7416723328422$$
$$x_{85} = -70.0287518186291$$
$$x_{86} = 74.2529128163118$$
$$x_{87} = 81.2627080522657$$
$$x_{88} = -13.7293201913147$$
$$x_{89} = 96.2525672823938$$
$$x_{90} = -79.996401145904$$
$$x_{91} = -61.7312872310352$$
$$x_{92} = -91.9970139691073$$
$$x_{93} = -64.029511570492$$
$$x_{94} = -7.72567614263021$$
$$x_{95} = 60.0022092224492$$
$$x_{96} = -1.74930740111531$$
$$x_{97} = 38.2620177957948$$
$$x_{98} = 80.2512610557666$$
$$x_{99} = 19.9745247856047$$
$$x_{100} = -47.7576816532727$$
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
$$\left[100.374735941116, \infty\right)$$
Convexa en los intervalos
$$\left[-1.74930740111531, 1.74930740111531\right]$$