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$$- \frac{2 x \left(\tan^{2}{\left(x \right)} + 1\right)^{2}}{\tan^{3}{\left(x \right)}} + \frac{2 x \left(\tan^{2}{\left(x \right)} + 1\right)}{\tan{\left(x \right)}} + \frac{2 \left(\tan^{2}{\left(x \right)} + 1\right)}{\tan^{2}{\left(x \right)}} - \frac{1}{\sin{\left(x \right)}} - \frac{2 \cos^{2}{\left(x \right)}}{\sin^{3}{\left(x \right)}} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 92.6607944977061$$
$$x_{2} = -95.8029181516704$$
$$x_{3} = 51.8266328805172$$
$$x_{4} = -20.34656296132$$
$$x_{5} = -14.0300500102832$$
$$x_{6} = 98.9450080712976$$
$$x_{7} = -89.518633555259$$
$$x_{8} = 48.663857552942$$
$$x_{9} = 89.529806214315$$
$$x_{10} = -17.2498182906398$$
$$x_{11} = -45.5201350631742$$
$$x_{12} = 29.7947645296798$$
$$x_{13} = -58.0936408404364$$
$$x_{14} = 95.8133577159511$$
$$x_{15} = 20.3958644244449$$
$$x_{16} = -67.5368394290771$$
$$x_{17} = 23.4980665179117$$
$$x_{18} = -23.5407226494946$$
$$x_{19} = 14.101791793788$$
$$x_{20} = 86.3764312526094$$
$$x_{21} = 76.962523847133$$
$$x_{22} = -7.65682782142835$$
$$x_{23} = 64.3948856648342$$
$$x_{24} = -64.3793478933585$$
$$x_{25} = 45.5421170536582$$
$$x_{26} = -61.2528948624257$$
$$x_{27} = 7.79027648865144$$
$$x_{28} = -80.1043712556991$$
$$x_{29} = -32.9411714066534$$
$$x_{30} = 58.1108610153877$$
$$x_{31} = -86.3880104889341$$
$$x_{32} = -51.8073213023768$$
$$x_{33} = 32.9715646685198$$
$$x_{34} = -42.399711295291$$
$$x_{35} = -4.60608445519679$$
$$x_{36} = 26.6848123501085$$
$$x_{37} = -70.6646060776428$$
$$x_{38} = 73.8071027130684$$
$$x_{39} = -92.6715881719091$$
$$x_{40} = 83.2461994371138$$
$$x_{41} = -10.950085744552$$
$$x_{42} = 42.3760961175032$$
$$x_{43} = -29.8283762733104$$
$$x_{44} = 61.2365591242938$$
$$x_{45} = -73.8206547568147$$
$$x_{46} = 36.0867370298432$$
$$x_{47} = 4.36177741523369$$
$$x_{48} = 17.1913959786094$$
$$x_{49} = -76.9495254808397$$
$$x_{50} = 1.24655273178117$$
$$x_{51} = 10.8569751785559$$
$$x_{52} = 54.9505707882264$$
$$x_{53} = 80.0918830820948$$
$$x_{54} = -98.955116028705$$
$$x_{55} = -36.1144755141436$$
$$x_{56} = -39.2316644332752$$
$$x_{57} = 70.6787610937535$$
$$x_{58} = 67.5220252515496$$
$$x_{59} = -48.6844178893469$$
$$x_{60} = -83.2341829026628$$
$$x_{61} = -26.6472167751449$$
$$x_{62} = -54.9687767442645$$
$$x_{63} = 39.2571754303557$$
Además hay que calcular los límites de y'' para los argumentos tendientes a los puntos de indeterminación de la función:
Puntos donde hay indeterminación:
$$x_{1} = 0$$
$$x_{2} = 3.14159265358979$$
$$\lim_{x \to 0^-}\left(- \frac{2 x \left(\tan^{2}{\left(x \right)} + 1\right)^{2}}{\tan^{3}{\left(x \right)}} + \frac{2 x \left(\tan^{2}{\left(x \right)} + 1\right)}{\tan{\left(x \right)}} + \frac{2 \left(\tan^{2}{\left(x \right)} + 1\right)}{\tan^{2}{\left(x \right)}} - \frac{1}{\sin{\left(x \right)}} - \frac{2 \cos^{2}{\left(x \right)}}{\sin^{3}{\left(x \right)}}\right) = \infty$$
$$\lim_{x \to 0^+}\left(- \frac{2 x \left(\tan^{2}{\left(x \right)} + 1\right)^{2}}{\tan^{3}{\left(x \right)}} + \frac{2 x \left(\tan^{2}{\left(x \right)} + 1\right)}{\tan{\left(x \right)}} + \frac{2 \left(\tan^{2}{\left(x \right)} + 1\right)}{\tan^{2}{\left(x \right)}} - \frac{1}{\sin{\left(x \right)}} - \frac{2 \cos^{2}{\left(x \right)}}{\sin^{3}{\left(x \right)}}\right) = -\infty$$
- los límites no son iguales, signo
$$x_{1} = 0$$
- es el punto de flexión
$$\lim_{x \to 3.14159265358979^-}\left(- \frac{2 x \left(\tan^{2}{\left(x \right)} + 1\right)^{2}}{\tan^{3}{\left(x \right)}} + \frac{2 x \left(\tan^{2}{\left(x \right)} + 1\right)}{\tan{\left(x \right)}} + \frac{2 \left(\tan^{2}{\left(x \right)} + 1\right)}{\tan^{2}{\left(x \right)}} - \frac{1}{\sin{\left(x \right)}} - \frac{2 \cos^{2}{\left(x \right)}}{\sin^{3}{\left(x \right)}}\right) = 2.33203094436526 \cdot 10^{48}$$
$$\lim_{x \to 3.14159265358979^+}\left(- \frac{2 x \left(\tan^{2}{\left(x \right)} + 1\right)^{2}}{\tan^{3}{\left(x \right)}} + \frac{2 x \left(\tan^{2}{\left(x \right)} + 1\right)}{\tan{\left(x \right)}} + \frac{2 \left(\tan^{2}{\left(x \right)} + 1\right)}{\tan^{2}{\left(x \right)}} - \frac{1}{\sin{\left(x \right)}} - \frac{2 \cos^{2}{\left(x \right)}}{\sin^{3}{\left(x \right)}}\right) = 2.33203094436526 \cdot 10^{48}$$
- los límites son iguales, es decir omitimos el punto correspondiente
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
$$\left[98.9450080712976, \infty\right)$$
Convexa en los intervalos
$$\left[-4.60608445519679, 1.24655273178117\right]$$