Para hallar los extremos hay que resolver la ecuación
$$\frac{d}{d x} f{\left(x \right)} = 0$$
(la derivada es igual a cero),
y las raíces de esta ecuación serán los extremos de esta función:
$$\frac{d}{d x} f{\left(x \right)} = $$
primera derivada$$\frac{x \cos{\left(x \right)}}{3} + \frac{\sin{\left(x \right)}}{3} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -64.4181717218392$$
$$x_{2} = -45.57503179559$$
$$x_{3} = 70.69997803861$$
$$x_{4} = -51.855560729152$$
$$x_{5} = -48.7152107175577$$
$$x_{6} = -7.97866571241324$$
$$x_{7} = 89.5465575382492$$
$$x_{8} = -42.4350618814099$$
$$x_{9} = 64.4181717218392$$
$$x_{10} = 36.1559664195367$$
$$x_{11} = -29.8785865061074$$
$$x_{12} = -98.9702722883957$$
$$x_{13} = 45.57503179559$$
$$x_{14} = -73.8409691490209$$
$$x_{15} = 98.9702722883957$$
$$x_{16} = 95.8290108090195$$
$$x_{17} = 14.2074367251912$$
$$x_{18} = 80.1230928148503$$
$$x_{19} = -20.469167402741$$
$$x_{20} = 73.8409691490209$$
$$x_{21} = -58.1366632448992$$
$$x_{22} = 4.91318043943488$$
$$x_{23} = -17.3363779239834$$
$$x_{24} = -61.2773745335697$$
$$x_{25} = 23.6042847729804$$
$$x_{26} = -39.295350981473$$
$$x_{27} = 58.1366632448992$$
$$x_{28} = -54.9960525574964$$
$$x_{29} = 83.2642147040886$$
$$x_{30} = 39.295350981473$$
$$x_{31} = 20.469167402741$$
$$x_{32} = 102.111554139654$$
$$x_{33} = 51.855560729152$$
$$x_{34} = 92.687771772017$$
$$x_{35} = 17.3363779239834$$
$$x_{36} = 0$$
$$x_{37} = -67.5590428388084$$
$$x_{38} = -11.085538406497$$
$$x_{39} = 7.97866571241324$$
$$x_{40} = -95.8290108090195$$
$$x_{41} = -14.2074367251912$$
$$x_{42} = 67.5590428388084$$
$$x_{43} = -70.69997803861$$
$$x_{44} = -23.6042847729804$$
$$x_{45} = 11.085538406497$$
$$x_{46} = -4.91318043943488$$
$$x_{47} = -76.9820093304187$$
$$x_{48} = 2.02875783811043$$
$$x_{49} = -26.7409160147873$$
$$x_{50} = 26.7409160147873$$
$$x_{51} = 54.9960525574964$$
$$x_{52} = -89.5465575382492$$
$$x_{53} = -36.1559664195367$$
$$x_{54} = -83.2642147040886$$
$$x_{55} = 86.4053708116885$$
$$x_{56} = 61.2773745335697$$
$$x_{57} = 76.9820093304187$$
$$x_{58} = -92.687771772017$$
$$x_{59} = 42.4350618814099$$
$$x_{60} = -86.4053708116885$$
$$x_{61} = 48.7152107175577$$
$$x_{62} = -33.0170010333572$$
$$x_{63} = 33.0170010333572$$
$$x_{64} = -80.1230928148503$$
$$x_{65} = -2.02875783811043$$
$$x_{66} = 29.8785865061074$$
Signos de extremos en los puntos:
(-64.41817172183916, 21.4701371131251)
(-45.57503179559002, 15.1880216120089)
(70.69997803861, 23.564302320531)
(-51.85556072915197, 17.2819737500672)
(-48.715210717557724, -16.234983408456)
(-7.978665712413241, 2.63890912386259)
(89.54655753824919, 29.8469914576284)
(-42.43506188140989, -14.1410946924197)
(64.41817172183916, 21.4701371131251)
(36.15596641953672, -12.0473817907474)
(-29.878586506107393, -9.9539553863956)
(-98.9702722883957, -32.9884068843729)
(45.57503179559002, 15.1880216120089)
(-73.8409691490209, -24.6113995905139)
(98.9702722883957, -32.9884068843729)
(95.82901080901948, 31.9412645361552)
(14.207436725191188, 4.72412470459143)
(80.12309281485025, -26.7056177152197)
(-20.46916740274095, 6.81492801941742)
(73.8409691490209, -24.6113995905139)
(-58.13666324489916, 19.3760215760286)
(4.913180439434884, -1.60482329657076)
(-17.33637792398336, -5.76920286928617)
(-61.277374533569656, -20.4230721814922)
(23.604284772980407, -7.86104354987779)
(-39.295350981472986, 13.0942110022973)
(58.13666324489916, 19.3760215760286)
(-54.99605255749639, -18.3289877498992)
(83.26421470408864, 27.7527367909844)
(39.295350981472986, 13.0942110022973)
(20.46916740274095, 6.81492801941742)
(102.11155413965392, 34.0355526287721)
(51.85556072915197, 17.2819737500672)
(92.687771772017, -30.8941259293531)
(17.33637792398336, -5.76920286928617)
(0, 0)
(-67.5590428388084, -22.5172143736575)
(-11.085538406497022, -3.68023600531)
(7.978665712413241, 2.63890912386259)
(-95.82901080901948, 31.9412645361552)
(-14.207436725191188, 4.72412470459143)
(67.5590428388084, -22.5172143736575)
(-70.69997803861, 23.564302320531)
(-23.604284772980407, -7.86104354987779)
(11.085538406497022, -3.68023600531)
(-4.913180439434884, -1.60482329657076)
(-76.98200933041872, 25.6585050427546)
(2.028757838110434, 0.606568580386551)
(-26.74091601478731, 8.90741255489913)
(26.74091601478731, 8.90741255489913)
(54.99605255749639, -18.3289877498992)
(-89.54655753824919, 29.8469914576284)
(-36.15596641953672, -12.0473817907474)
(-83.26421470408864, 27.7527367909844)
(86.40537081168854, -28.7998615718702)
(61.277374533569656, -20.4230721814922)
(76.98200933041872, 25.6585050427546)
(-92.687771772017, -30.8941259293531)
(42.43506188140989, -14.1410946924197)
(-86.40537081168854, -28.7998615718702)
(48.715210717557724, -16.234983408456)
(-33.017001033357246, 11.0006225769485)
(33.017001033357246, 11.0006225769485)
(-80.12309281485025, -26.7056177152197)
(-2.028757838110434, 0.606568580386551)
(29.878586506107393, -9.9539553863956)
Intervalos de crecimiento y decrecimiento de la función:Hallemos los intervalos donde la función crece y decrece y también los puntos mínimos y máximos de la función, para lo cual miramos cómo se comporta la función en los extremos con desviación mínima del extremo:
Puntos mínimos de la función:
$$x_{1} = -48.7152107175577$$
$$x_{2} = -42.4350618814099$$
$$x_{3} = 36.1559664195367$$
$$x_{4} = -29.8785865061074$$
$$x_{5} = -98.9702722883957$$
$$x_{6} = -73.8409691490209$$
$$x_{7} = 98.9702722883957$$
$$x_{8} = 80.1230928148503$$
$$x_{9} = 73.8409691490209$$
$$x_{10} = 4.91318043943488$$
$$x_{11} = -17.3363779239834$$
$$x_{12} = -61.2773745335697$$
$$x_{13} = 23.6042847729804$$
$$x_{14} = -54.9960525574964$$
$$x_{15} = 92.687771772017$$
$$x_{16} = 17.3363779239834$$
$$x_{17} = 0$$
$$x_{18} = -67.5590428388084$$
$$x_{19} = -11.085538406497$$
$$x_{20} = 67.5590428388084$$
$$x_{21} = -23.6042847729804$$
$$x_{22} = 11.085538406497$$
$$x_{23} = -4.91318043943488$$
$$x_{24} = 54.9960525574964$$
$$x_{25} = -36.1559664195367$$
$$x_{26} = 86.4053708116885$$
$$x_{27} = 61.2773745335697$$
$$x_{28} = -92.687771772017$$
$$x_{29} = 42.4350618814099$$
$$x_{30} = -86.4053708116885$$
$$x_{31} = 48.7152107175577$$
$$x_{32} = -80.1230928148503$$
$$x_{33} = 29.8785865061074$$
Puntos máximos de la función:
$$x_{33} = -64.4181717218392$$
$$x_{33} = -45.57503179559$$
$$x_{33} = 70.69997803861$$
$$x_{33} = -51.855560729152$$
$$x_{33} = -7.97866571241324$$
$$x_{33} = 89.5465575382492$$
$$x_{33} = 64.4181717218392$$
$$x_{33} = 45.57503179559$$
$$x_{33} = 95.8290108090195$$
$$x_{33} = 14.2074367251912$$
$$x_{33} = -20.469167402741$$
$$x_{33} = -58.1366632448992$$
$$x_{33} = -39.295350981473$$
$$x_{33} = 58.1366632448992$$
$$x_{33} = 83.2642147040886$$
$$x_{33} = 39.295350981473$$
$$x_{33} = 20.469167402741$$
$$x_{33} = 102.111554139654$$
$$x_{33} = 51.855560729152$$
$$x_{33} = 7.97866571241324$$
$$x_{33} = -95.8290108090195$$
$$x_{33} = -14.2074367251912$$
$$x_{33} = -70.69997803861$$
$$x_{33} = -76.9820093304187$$
$$x_{33} = 2.02875783811043$$
$$x_{33} = -26.7409160147873$$
$$x_{33} = 26.7409160147873$$
$$x_{33} = -89.5465575382492$$
$$x_{33} = -83.2642147040886$$
$$x_{33} = 76.9820093304187$$
$$x_{33} = -33.0170010333572$$
$$x_{33} = 33.0170010333572$$
$$x_{33} = -2.02875783811043$$
Decrece en los intervalos
$$\left[98.9702722883957, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -98.9702722883957\right]$$