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$$\frac{2 \left(- \sin{\left(x \right)} \operatorname{atan}{\left(\sin{\left(x \right)} - 4 \right)} - \frac{2 \left(\sin{\left(x \right)} - 4\right) \cos^{2}{\left(x \right)} \operatorname{atan}{\left(\sin{\left(x \right)} - 4 \right)}}{\left(\sin{\left(x \right)} - 4\right)^{2} + 1} + \frac{\cos^{2}{\left(x \right)}}{\left(\sin{\left(x \right)} - 4\right)^{2} + 1}\right)}{\left(\sin{\left(x \right)} - 4\right)^{2} + 1} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -41.2411773060209$$
$$x_{2} = -28.6748066916618$$
$$x_{3} = 565.887150455516$$
$$x_{4} = 59.2897876088524$$
$$x_{5} = 38.0995846524311$$
$$x_{6} = -85.2234744562781$$
$$x_{7} = 100.931437724227$$
$$x_{8} = 50.6659552667903$$
$$x_{9} = -16.1084360773026$$
$$x_{10} = -9.82525077012301$$
$$x_{11} = -22.3916213844822$$
$$x_{12} = 6.68365811653322$$
$$x_{13} = 2.74111984423616$$
$$x_{14} = -66.3739185347393$$
$$x_{15} = -87.5641214911606$$
$$x_{16} = 40.4402316873137$$
$$x_{17} = -49.8650096480831$$
$$x_{18} = 84.4225288375708$$
$$x_{19} = -56.1481949552626$$
$$x_{20} = -43.5818243409035$$
$$x_{21} = -8682.96162171284$$
$$x_{22} = -5.88271249782596$$
$$x_{23} = -37.2986390337239$$
$$x_{24} = 78.1393435303912$$
$$x_{25} = 46.7234169944933$$
$$x_{26} = -3.54206546294342$$
$$x_{27} = -18.4490831121851$$
$$x_{28} = 94.6482524170474$$
$$x_{29} = -100.13049210552$$
$$x_{30} = 31.8163993452516$$
$$x_{31} = -97.7898450706372$$
$$x_{32} = 90.7057141447504$$
$$x_{33} = -104.073030377817$$
$$x_{34} = -47.5243626132005$$
$$x_{35} = -68.7145655696218$$
$$x_{36} = 9.02430515141575$$
$$x_{37} = 21.5906757657749$$
$$x_{38} = 53.0066023016729$$
$$x_{39} = 65.572972916032$$
$$x_{40} = -81.280936183981$$
$$x_{41} = -60.0907332275597$$
$$x_{42} = -78.9402891490985$$
$$x_{43} = -53.8075479203801$$
$$x_{44} = 27.8738610729545$$
$$x_{45} = 34.1570463801341$$
$$x_{46} = -34.9579919988414$$
$$x_{47} = -72.6571038419189$$
$$x_{48} = 12.9668434237128$$
$$x_{49} = 63.2323258811495$$
$$x_{50} = -12.1658978050055$$
$$x_{51} = 157.480105488843$$
$$x_{52} = 75.7986964955087$$
$$x_{53} = -62.4313802624422$$
$$x_{54} = -411.949110429617$$
$$x_{55} = 56.9491405739699$$
$$x_{56} = 69.5155111883291$$
$$x_{57} = 0.400472809353631$$
$$x_{58} = -93.8473067983402$$
$$x_{59} = 96.98889945193$$
$$x_{60} = -24.7322684193647$$
$$x_{61} = 88.3650671098678$$
$$x_{62} = 44.3827699596107$$
$$x_{63} = 15.3074904585953$$
$$x_{64} = 71.8561582232116$$
$$x_{65} = 82.0818818026883$$
$$x_{66} = -91.5066597634576$$
$$x_{67} = 25.533214038072$$
$$x_{68} = 19.2500287308924$$
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
$$\left[565.887150455516, \infty\right)$$
Convexa en los intervalos
$$\left(-\infty, -8682.96162171284\right]$$