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$$2 \left(\frac{x}{\left(x^{2} + 1\right)^{2} \operatorname{acot}^{2}{\left(x \right)}} - \frac{1}{\left(x^{2} + 1\right)^{2} \operatorname{acot}^{3}{\left(x \right)}} + \frac{1}{x^{3}}\right) = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 30577.6412615909$$
$$x_{2} = -11796.3780998675$$
$$x_{3} = -23665.0705139377$$
$$x_{4} = 42444.5833091172$$
$$x_{5} = 10231.72559016$$
$$x_{6} = 17862.3508392429$$
$$x_{7} = -15187.7870357588$$
$$x_{8} = 11079.7200445038$$
$$x_{9} = -21121.989701487$$
$$x_{10} = 17014.5998807393$$
$$x_{11} = 31425.2920541568$$
$$x_{12} = -34684.6338309128$$
$$x_{13} = -17731.0961300007$$
$$x_{14} = -12644.2797840166$$
$$x_{15} = -13492.1444025026$$
$$x_{16} = 22100.9373832686$$
$$x_{17} = -22817.3835311773$$
$$x_{18} = 37358.7885164166$$
$$x_{19} = 16166.8336152296$$
$$x_{20} = -16883.3429620852$$
$$x_{21} = 40749.3230717359$$
$$x_{22} = -38922.820762134$$
$$x_{23} = 14471.2444887927$$
$$x_{24} = -35532.274376819$$
$$x_{25} = -39770.4539132995$$
$$x_{26} = 34815.872583604$$
$$x_{27} = -10948.4308616174$$
$$x_{28} = -30446.4008184081$$
$$x_{29} = -37227.5505136143$$
$$x_{30} = 28034.6720206192$$
$$x_{31} = 33120.5864999895$$
$$x_{32} = 12775.5551119178$$
$$x_{33} = 18710.0885593082$$
$$x_{34} = -32989.3471485563$$
$$x_{35} = 28882.3314917342$$
$$x_{36} = -31294.0520044611$$
$$x_{37} = 33968.2305089527$$
$$x_{38} = -24512.7517881137$$
$$x_{39} = 21253.2380542817$$
$$x_{40} = 36511.1514680498$$
$$x_{41} = -16035.5741315916$$
$$x_{42} = -36379.9132326258$$
$$x_{43} = 39901.6913050112$$
$$x_{44} = 32272.9404045665$$
$$x_{45} = -27055.7667092598$$
$$x_{46} = 19557.8147532723$$
$$x_{47} = -21969.6901815189$$
$$x_{48} = -19426.5636338291$$
$$x_{49} = -33836.9914680973$$
$$x_{50} = 27187.0091116588$$
$$x_{51} = 11927.6596236541$$
$$x_{52} = -26208.0994197283$$
$$x_{53} = 22948.6297069588$$
$$x_{54} = -20274.2812005966$$
$$x_{55} = 38206.4241103144$$
$$x_{56} = 24643.9962202423$$
$$x_{57} = 15319.0495203894$$
$$x_{58} = -42313.3464219447$$
$$x_{59} = 35663.5128616544$$
$$x_{60} = -41465.7166723032$$
$$x_{61} = -28751.0901550954$$
$$x_{62} = 41596.9537174076$$
$$x_{63} = -27903.4301752598$$
$$x_{64} = -14339.9784626787$$
$$x_{65} = 23796.3157713546$$
$$x_{66} = 26339.3424338007$$
$$x_{67} = -25360.4279243482$$
$$x_{68} = 39054.0583443264$$
$$x_{69} = -18578.8357666369$$
$$x_{70} = 25491.6716121075$$
$$x_{71} = -32141.7007177568$$
$$x_{72} = -38075.1863248175$$
$$x_{73} = 20405.5308506781$$
$$x_{74} = -29598.7469475975$$
$$x_{75} = 13623.4146482641$$
$$x_{76} = 29729.9878184065$$
$$x_{77} = -40618.085858737$$
Además hay que calcular los límites de y'' para los argumentos tendientes a los puntos de indeterminación de la función:
Puntos donde hay indeterminación:
$$x_{1} = 0$$
$$\lim_{x \to 0^-}\left(2 \left(\frac{x}{\left(x^{2} + 1\right)^{2} \operatorname{acot}^{2}{\left(x \right)}} - \frac{1}{\left(x^{2} + 1\right)^{2} \operatorname{acot}^{3}{\left(x \right)}} + \frac{1}{x^{3}}\right)\right) = -\infty$$
$$\lim_{x \to 0^+}\left(2 \left(\frac{x}{\left(x^{2} + 1\right)^{2} \operatorname{acot}^{2}{\left(x \right)}} - \frac{1}{\left(x^{2} + 1\right)^{2} \operatorname{acot}^{3}{\left(x \right)}} + \frac{1}{x^{3}}\right)\right) = \infty$$
- los límites no son iguales, signo
$$x_{1} = 0$$
- es el punto de flexión
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
$$\left[31425.2920541568, \infty\right)$$
Convexa en los intervalos
$$\left(-\infty, -39770.4539132995\right]$$