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$$2 \left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} - \frac{1}{2 x^{3}} = 0$$
Solve this equationThe roots of this equation
$$x_{1} = 59.6902615937248$$
$$x_{2} = 31.4159345987753$$
$$x_{3} = -12.566496593124$$
$$x_{4} = -21.9911720820024$$
$$x_{5} = 28.2743449424922$$
$$x_{6} = 9.42507655767126$$
$$x_{7} = -6.28419268165633$$
$$x_{8} = -25.1327569765083$$
$$x_{9} = 78.5398168557694$$
$$x_{10} = -15.7080277702229$$
$$x_{11} = 34.5575252472483$$
$$x_{12} = 69.1150391361959$$
$$x_{13} = 84.8230020565613$$
$$x_{14} = -69.1150391361959$$
$$x_{15} = 100.530965160933$$
$$x_{16} = -40.8407081666179$$
$$x_{17} = 56.5486691471408$$
$$x_{18} = -18.8495932494818$$
$$x_{19} = -56.5486691471408$$
$$x_{20} = 40.8407081666179$$
$$x_{21} = -43.9823000886252$$
$$x_{22} = -47.1238921928491$$
$$x_{23} = -53.4070767521588$$
$$x_{24} = -3.14959356380938$$
$$x_{25} = -78.5398168557694$$
$$x_{26} = -75.3982242694076$$
$$x_{27} = 87.9645946678103$$
$$x_{28} = 25.1327569765083$$
$$x_{29} = -87.9645946678103$$
$$x_{30} = 75.3982242694076$$
$$x_{31} = -100.530965160933$$
$$x_{32} = 6.28419268165633$$
$$x_{33} = 65.9734465960134$$
$$x_{34} = -31.4159345987753$$
$$x_{35} = 47.1238921928491$$
$$x_{36} = -34.5575252472483$$
$$x_{37} = -72.2566316952498$$
$$x_{38} = -62.8318540796563$$
$$x_{39} = -50.2654844259139$$
$$x_{40} = 97.3893725319319$$
$$x_{41} = -97.3893725319319$$
$$x_{42} = -91.1061872846991$$
$$x_{43} = 12.566496593124$$
$$x_{44} = -37.6991165090964$$
$$x_{45} = 15.7080277702229$$
$$x_{46} = 50.2654844259139$$
$$x_{47} = 3.14959356380938$$
$$x_{48} = 43.9823000886252$$
$$x_{49} = 94.2477799063191$$
$$x_{50} = 53.4070767521588$$
$$x_{51} = -84.8230020565613$$
$$x_{52} = 72.2566316952498$$
$$x_{53} = -59.6902615937248$$
$$x_{54} = 21.9911720820024$$
$$x_{55} = -65.9734465960134$$
$$x_{56} = -81.6814094520786$$
$$x_{57} = 91.1061872846991$$
$$x_{58} = 18.8495932494818$$
$$x_{59} = 62.8318540796563$$
$$x_{60} = 37.6991165090964$$
$$x_{61} = -28.2743449424922$$
$$x_{62} = 81.6814094520786$$
$$x_{63} = -9.42507655767126$$
$$x_{64} = -94.2477799063191$$
You also need to calculate the limits of y '' for arguments seeking to indeterminate points of a function:
Points where there is an indetermination:
$$x_{1} = 0$$
$$\lim_{x \to 0^-}\left(2 \left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} - \frac{1}{2 x^{3}}\right) = \infty$$
$$\lim_{x \to 0^+}\left(2 \left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} - \frac{1}{2 x^{3}}\right) = -\infty$$
- the limits are not equal, so
$$x_{1} = 0$$
- is an inflection point
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
$$\left[100.530965160933, \infty\right)$$
Convex at the intervals
$$\left(-\infty, -100.530965160933\right]$$