Let's find the inflection points, we'll need to solve the equation for this
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0$$
(the second derivative equals zero),
the roots of this equation will be the inflection points for the specified function graph:
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = $$
the second derivative$$2 \left(- \frac{x}{\left(x^{2} + 1\right)^{2}} + \left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)}\right) = 0$$
Solve this equationThe roots of this equation
$$x_{1} = -91.1061882761657$$
$$x_{2} = 34.5575433799626$$
$$x_{3} = -97.3893733436485$$
$$x_{4} = -25.1328040205507$$
$$x_{5} = -94.2477808019261$$
$$x_{6} = 31.4159587220774$$
$$x_{7} = 0$$
$$x_{8} = -21.9912422140771$$
$$x_{9} = 78.5398184031738$$
$$x_{10} = 9.42594558462241$$
$$x_{11} = 25.1328040205507$$
$$x_{12} = -53.4070816709532$$
$$x_{13} = -9.42594558462241$$
$$x_{14} = 40.8407191588716$$
$$x_{15} = 59.6902651176419$$
$$x_{16} = 3.16758836114823$$
$$x_{17} = -43.98230889158$$
$$x_{18} = 75.3982260183446$$
$$x_{19} = -75.3982260183446$$
$$x_{20} = -34.5575433799626$$
$$x_{21} = 37.6991304808952$$
$$x_{22} = -62.8318571011953$$
$$x_{23} = 91.1061882761657$$
$$x_{24} = -59.6902651176419$$
$$x_{25} = 94.2477808019261$$
$$x_{26} = 87.9645957693188$$
$$x_{27} = 18.8497043937593$$
$$x_{28} = -78.5398184031738$$
$$x_{29} = -87.9645957693188$$
$$x_{30} = -37.6991304808952$$
$$x_{31} = -56.548673291256$$
$$x_{32} = 53.4070816709532$$
$$x_{33} = 84.8230032850167$$
$$x_{34} = 15.7082191890374$$
$$x_{35} = 97.3893733436485$$
$$x_{36} = -65.9734492062964$$
$$x_{37} = -72.2566336822883$$
$$x_{38} = 6.28701317511834$$
$$x_{39} = -31.4159587220774$$
$$x_{40} = -47.1238993512507$$
$$x_{41} = 72.2566336822883$$
$$x_{42} = -18.8497043937593$$
$$x_{43} = 12.5668681635809$$
$$x_{44} = -12.5668681635809$$
$$x_{45} = -69.1150414065892$$
$$x_{46} = 100.530965898917$$
$$x_{47} = 56.548673291256$$
$$x_{48} = 62.8318571011953$$
$$x_{49} = -28.2743780124173$$
$$x_{50} = -6.28701317511834$$
$$x_{51} = -84.8230032850167$$
$$x_{52} = -3.16758836114823$$
$$x_{53} = 47.1238993512507$$
$$x_{54} = -40.8407191588716$$
$$x_{55} = -15.7082191890374$$
$$x_{56} = 65.9734492062964$$
$$x_{57} = -81.6814108277603$$
$$x_{58} = 28.2743780124173$$
$$x_{59} = -50.2654903251137$$
$$x_{60} = 21.9912422140771$$
$$x_{61} = 81.6814108277603$$
$$x_{62} = 69.1150414065892$$
$$x_{63} = 50.2654903251137$$
$$x_{64} = -100.530965898917$$
$$x_{65} = 43.98230889158$$
Сonvexity and concavity intervals:Let’s find the intervals where the function is convex or concave, for this look at the behaviour of the function at the inflection points:
Concave at the intervals
$$\left[100.530965898917, \infty\right)$$
Convex at the intervals
$$\left(-\infty, -100.530965898917\right]$$