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$$\left(\frac{1}{3} - \frac{1}{3 \left(x^{2} + 1\right)}\right) \sin^{3}{\left(x \right)} + 3 \left(\frac{x}{3} + \frac{\left(-1\right) \operatorname{atan}{\left(x \right)}}{3}\right) \sin^{2}{\left(x \right)} \cos{\left(x \right)} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -47.1238897398428$$
$$x_{2} = 72.2566310277228$$
$$x_{3} = 15.7079634238123$$
$$x_{4} = 97.3893722386395$$
$$x_{5} = -42.4196515709562$$
$$x_{6} = 14.1633536976303$$
$$x_{7} = -43.982297174703$$
$$x_{8} = 95.8221117869534$$
$$x_{9} = 34.5575190521566$$
$$x_{10} = -36.1379432026438$$
$$x_{11} = 37.6991119965993$$
$$x_{12} = 40.8407044980859$$
$$x_{13} = -34.5575191251925$$
$$x_{14} = 12.5663704809964$$
$$x_{15} = -51.8429042612973$$
$$x_{16} = 36.1379432026438$$
$$x_{17} = -7.9047266518689$$
$$x_{18} = -78.5398162431523$$
$$x_{19} = 56.5486676281888$$
$$x_{20} = -59.6902604573859$$
$$x_{21} = -100.530964808226$$
$$x_{22} = -53.407075259837$$
$$x_{23} = 18.8495559923432$$
$$x_{24} = -29.8568869013277$$
$$x_{25} = -31.4159266845618$$
$$x_{26} = -12.5663706164231$$
$$x_{27} = -65.9734457652762$$
$$x_{28} = 20.4379300963978$$
$$x_{29} = 58.1253545010966$$
$$x_{30} = 6.28318528466365$$
$$x_{31} = -23.577034707719$$
$$x_{32} = -9.42477811595977$$
$$x_{33} = -3.14159285481255$$
$$x_{34} = 4.80501573129414$$
$$x_{35} = -95.8221117869534$$
$$x_{36} = -87.9645943592141$$
$$x_{37} = -45.5606634099038$$
$$x_{38} = 94.2477796093528$$
$$x_{39} = -80.1148552083624$$
$$x_{40} = -43.9822972046548$$
$$x_{41} = 73.8320385087492$$
$$x_{42} = 21.9911485851914$$
$$x_{43} = -15.7079632965462$$
$$x_{44} = 51.8429042612973$$
$$x_{45} = -6.28318518053504$$
$$x_{46} = -21.9911485864908$$
$$x_{47} = -89.5391788958977$$
$$x_{48} = -73.8320385087492$$
$$x_{49} = 62.8318530430108$$
$$x_{50} = 64.4079514776374$$
$$x_{51} = 75.398223692586$$
$$x_{52} = 53.4070751439253$$
$$x_{53} = 7.9047266518689$$
$$x_{54} = 0$$
$$x_{55} = -25.1327412189989$$
$$x_{56} = 80.1148552083624$$
$$x_{57} = 28.2743338652787$$
$$x_{58} = -67.549291920442$$
$$x_{59} = -14.1633536976303$$
$$x_{60} = 65.9734457527599$$
$$x_{61} = -69.1150382652533$$
$$x_{62} = -1.88455017054346$$
$$x_{63} = 1.88455017054346$$
$$x_{64} = 9.42477807889789$$
$$x_{65} = 92.680640992997$$
$$x_{66} = -87.9645942994217$$
$$x_{67} = -28.2743337405708$$
$$x_{68} = 84.8230015969263$$
$$x_{69} = -37.6991118770157$$
$$x_{70} = -81.6814090376207$$
$$x_{71} = -58.1253545010966$$
$$x_{72} = 87.9645943354964$$
$$x_{73} = -50.2654823161497$$
$$x_{74} = 43.9822971693753$$
$$x_{75} = 29.8568869013277$$
$$x_{76} = 31.41592659636$$
$$x_{77} = 86.397726460829$$
$$x_{78} = 42.4196515709562$$
$$x_{79} = -56.5486676809069$$
$$x_{80} = 50.2654824463717$$
$$x_{81} = 21.9911485108066$$
Signos de extremos en los puntos:
(-47.12388973984283, 3.98310346097366e-21)
(72.25663102772283, 2.67597069160318e-24)
(15.707963423812345, -1.79234694014091e-20)
(97.38937223863952, 3.70884132285647e-22)
(-42.419651570956205, -13.622783998703)
(14.163353697630292, 4.21667496713117)
(-43.982297174703014, 2.06639646233012e-22)
(95.82211178695336, 31.4199944574926)
(34.557519052156564, 2.85040058445483e-20)
(-36.13794320264376, -11.5300006037631)
(37.699111996599285, 4.36068792687663e-20)
(40.84070449808586, -3.73890091284254e-26)
(-34.55751912519251, 2.92505830313435e-21)
(12.566370480996397, -8.75640298167247e-21)
(-51.842904261297335, 16.7626944041327)
(36.13794320264376, -11.5300006037631)
(-7.904726651868903, 2.14495149966393)
(-78.53981624315229, 2.31258304446127e-20)
(56.54866762818882, -4.65491461069023e-20)
(-59.69026045738589, -1.16550125376709e-21)
(-100.5309648082264, -4.00155274285572e-20)
(-53.40707525983695, -5.69599789226226e-20)
(18.849555992343227, 2.05070614248904e-21)
(-29.85688690132773, -9.43790005122283)
(-31.41592668456182, 3.27213702463331e-20)
(-12.566370616423054, 3.24545686181302e-26)
(-65.97344576527618, -1.36299383969224e-21)
(20.43793009639784, 6.30241932128866)
(58.12535450109656, 18.8562721445462)
(6.283185284663652, -1.8530931632127e-23)
(-23.577034707718983, -7.34703244897591)
(-9.424778115959775, -9.91675067455694e-21)
(-3.1415928548125533, -5.10303885725562e-21)
(4.805015731294137, -1.13178788432727)
(-95.82211178695336, 31.4199944574926)
(-87.96459435921413, 5.82547059105447e-21)
(-45.560663409903775, 14.6693431242966)
(94.24777960935283, 1.41080617543143e-25)
(-80.1148552083624, -26.1848064691713)
(-43.98229720465481, 2.276863022088e-21)
(73.83203850874915, -24.0908268341739)
(21.991148585191436, -6.95143729038979e-24)
(-15.707963296546192, -1.1070354004941e-22)
(51.842904261297335, 16.7626944041327)
(-6.28318518053504, -3.29751523230015e-21)
(-21.991148586490784, -1.00068687626426e-23)
(-89.53917889589773, 29.3258855090146)
(-73.83203850874915, -24.0908268341739)
(62.83185304301077, -4.87168450060204e-22)
(64.40795147763735, 20.9500098681499)
(75.39822369258601, 6.54644327525439e-24)
(53.40707514392534, -6.15476868236516e-22)
(7.904726651868903, 2.14495149966393)
(0, 0)
(-25.132741218998916, -7.22344924354435e-24)
(80.1148552083624, -26.1848064691713)
(28.27433386527867, 4.40175054211864e-23)
(-67.54929192044199, -21.996924731538)
(-14.163353697630292, 4.21667496713117)
(65.97344575275994, -4.40466653095097e-22)
(-69.11503826525328, -3.31203997990776e-20)
(-1.8845501705434633, 0.22994789474801)
(1.8845501705434633, 0.22994789474801)
(9.424778078897885, -4.37359944257925e-21)
(92.68064099299698, -30.3729351221931)
(-87.96459429942173, -3.75539371192506e-26)
(-28.27433374057076, 2.53790472959541e-20)
(84.82300159692633, 3.46893455991417e-21)
(-37.699111877015746, 4.71099422940883e-22)
(-81.68140903762065, 2.31971907254417e-21)
(-58.12535450109656, 18.8562721445462)
(87.96459433549641, 1.23299113518815e-21)
(-50.26548231614965, -4.57978063086762e-20)
(43.98229716937529, 9.88405807000468e-23)
(29.85688690132773, -9.43790005122283)
(31.415926596359974, 2.20121989284558e-21)
(86.39772646082896, -28.2788466810656)
(42.419651570956205, -13.622783998703)
(-56.54866768090694, -1.07529612384756e-20)
(50.26548244637171, -2.19983144722745e-23)
(21.99114851080661, 1.81545208169053e-21)
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:
$$x_{1} = -42.4196515709562$$
$$x_{2} = -36.1379432026438$$
$$x_{3} = 36.1379432026438$$
$$x_{4} = -29.8568869013277$$
$$x_{5} = -23.577034707719$$
$$x_{6} = 4.80501573129414$$
$$x_{7} = -80.1148552083624$$
$$x_{8} = 73.8320385087492$$
$$x_{9} = -73.8320385087492$$
$$x_{10} = 0$$
$$x_{11} = 80.1148552083624$$
$$x_{12} = -67.549291920442$$
$$x_{13} = 92.680640992997$$
$$x_{14} = 29.8568869013277$$
$$x_{15} = 86.397726460829$$
$$x_{16} = 42.4196515709562$$
Puntos máximos de la función:
$$x_{16} = 14.1633536976303$$
$$x_{16} = 95.8221117869534$$
$$x_{16} = -51.8429042612973$$
$$x_{16} = -7.9047266518689$$
$$x_{16} = 20.4379300963978$$
$$x_{16} = 58.1253545010966$$
$$x_{16} = -95.8221117869534$$
$$x_{16} = -45.5606634099038$$
$$x_{16} = 51.8429042612973$$
$$x_{16} = -89.5391788958977$$
$$x_{16} = 64.4079514776374$$
$$x_{16} = 7.9047266518689$$
$$x_{16} = -14.1633536976303$$
$$x_{16} = -1.88455017054346$$
$$x_{16} = 1.88455017054346$$
$$x_{16} = -58.1253545010966$$
Decrece en los intervalos
$$\left[92.680640992997, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -80.1148552083624\right]$$