Hallemos los puntos de flexiones, para eso hay que resolver la ecuación
$$\frac{d^{2}}{d t^{2}} f{\left(t \right)} = 0$$
(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:
$$\frac{d^{2}}{d t^{2}} f{\left(t \right)} = $$
segunda derivada$$3 \left(- t \sin{\left(t \right)} + \cos{\left(t \right)}\right) = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$t_{1} = 59.7070073053355$$
$$t_{2} = -25.1724463266467$$
$$t_{3} = 31.4477146375462$$
$$t_{4} = 97.3996388790738$$
$$t_{5} = -56.5663442798215$$
$$t_{6} = -47.145097736761$$
$$t_{7} = 18.90240995686$$
$$t_{8} = 44.0050179208308$$
$$t_{9} = 56.5663442798215$$
$$t_{10} = -28.309642854452$$
$$t_{11} = -147.661626855354$$
$$t_{12} = -81.6936492356017$$
$$t_{13} = -91.1171613944647$$
$$t_{14} = -12.6452872238566$$
$$t_{15} = 72.270467060309$$
$$t_{16} = 6.43729817917195$$
$$t_{17} = 65.9885986984904$$
$$t_{18} = -34.5864242152889$$
$$t_{19} = 37.7256128277765$$
$$t_{20} = -40.8651703304881$$
$$t_{21} = 78.5525459842429$$
$$t_{22} = -9.52933440536196$$
$$t_{23} = 22.0364967279386$$
$$t_{24} = -59.7070073053355$$
$$t_{25} = -100.540910786842$$
$$t_{26} = 15.7712848748159$$
$$t_{27} = -84.8347887180423$$
$$t_{28} = 75.4114834888481$$
$$t_{29} = 3.42561845948173$$
$$t_{30} = 28.309642854452$$
$$t_{31} = 94.2583883450399$$
$$t_{32} = 100.540910786842$$
$$t_{33} = -69.1295029738953$$
$$t_{34} = -44.0050179208308$$
$$t_{35} = 9.52933440536196$$
$$t_{36} = -18.90240995686$$
$$t_{37} = 12.6452872238566$$
$$t_{38} = 34.5864242152889$$
$$t_{39} = -116.247530303932$$
$$t_{40} = 81.6936492356017$$
$$t_{41} = -22.0364967279386$$
$$t_{42} = 69.1295029738953$$
$$t_{43} = -72.270467060309$$
$$t_{44} = -37.7256128277765$$
$$t_{45} = 84.8347887180423$$
$$t_{46} = 0.86033358901938$$
$$t_{47} = -78.5525459842429$$
$$t_{48} = -87.9759605524932$$
$$t_{49} = -75.4114834888481$$
$$t_{50} = 53.4257904773947$$
$$t_{51} = -65.9885986984904$$
$$t_{52} = -97.3996388790738$$
$$t_{53} = -6.43729817917195$$
$$t_{54} = -31.4477146375462$$
$$t_{55} = 47.145097736761$$
$$t_{56} = 25.1724463266467$$
$$t_{57} = 62.8477631944545$$
$$t_{58} = -62.8477631944545$$
$$t_{59} = -0.86033358901938$$
$$t_{60} = 50.2853663377737$$
$$t_{61} = 91.1171613944647$$
$$t_{62} = -3.42561845948173$$
$$t_{63} = 40.8651703304881$$
$$t_{64} = 87.9759605524932$$
$$t_{65} = -53.4257904773947$$
$$t_{66} = -15.7712848748159$$
$$t_{67} = -94.2583883450399$$
$$t_{68} = -50.2853663377737$$
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
$$\left[97.3996388790738, \infty\right)$$
Convexa en los intervalos
$$\left(-\infty, -100.540910786842\right]$$