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$$\log{\left(x \right)}^{3} \cos{\left(x \right)} + \frac{3 \log{\left(x \right)}^{2} \sin{\left(x \right)}}{x} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 61.2729534415634$$
$$x_{2} = 64.4138302477556$$
$$x_{3} = 58.1321658716346$$
$$x_{4} = 89.5428444653399$$
$$x_{5} = 83.2603534390183$$
$$x_{6} = 20.4688629160207$$
$$x_{7} = 36.1514414910436$$
$$x_{8} = 5.06267917117524$$
$$x_{9} = 45.5703287126706$$
$$x_{10} = 54.9914846404513$$
$$x_{11} = 73.8368718590989$$
$$x_{12} = 8.03139099623953$$
$$x_{13} = 42.4303637527494$$
$$x_{14} = 14.2164990994671$$
$$x_{15} = 98.9667658004856$$
$$x_{16} = 29.8746827273128$$
$$x_{17} = 23.60213003453$$
$$x_{18} = 95.8254375766894$$
$$x_{19} = 17.3393298030427$$
$$x_{20} = 48.7105340009097$$
$$x_{21} = 33.0127041187522$$
$$x_{22} = 2.49249324020916$$
$$x_{23} = 39.2907044598106$$
$$x_{24} = 11.1072905657786$$
$$x_{25} = 26.7376687721596$$
$$x_{26} = 86.4015846605975$$
$$x_{27} = 51.8509314096671$$
$$x_{28} = 70.6957994975412$$
$$x_{29} = 76.9779922603215$$
$$x_{30} = 80.1191545145906$$
$$x_{31} = 67.5547826177155$$
$$x_{32} = 92.6841296797232$$
Signos de extremos en los puntos:
(61.272953441563416, -69.6924873395813)
(64.41383024775558, 72.2637650284379)
(58.13216587163458, 67.0525603965331)
(89.54284446533988, 90.8019251907425)
(83.26035343901827, 86.463675148813)
(20.468862916020687, 27.4812868432645)
(36.15144149104357, -46.1677094492915)
(5.062679171175242, -4.00738236246644)
(45.57032871267055, 55.7021656471767)
(54.99148464045134, -64.3392173341535)
(73.83687185909886, -79.6065697917808)
(8.031390996239526, 8.9006328028635)
(42.4303637527494, -52.634958189165)
(14.216499099467082, 18.6437213828936)
(98.96676580048565, -97.0031586507996)
(29.87468272731276, -39.1833294541818)
(23.602130034530013, -31.5690573732181)
(95.82543757668938, 94.9743773579989)
(17.33932980304268, -23.1791662900454)
(48.71053400090973, -58.6703593940542)
(33.012704118752204, 42.7464677559037)
(2.4924932402091593, 0.460459077966658)
(39.29070445981061, 49.4600967590969)
(11.107290565778559, -13.8687767133005)
(26.737668772159612, 35.4632686286516)
(86.4015846605975, -88.6545457182069)
(51.85093140966714, 61.5471381349689)
(70.69579949754117, 77.217113333416)
(76.97799226032154, 81.9422464140317)
(80.11915451459063, -84.227058638229)
(67.5547826177155, -74.7706823820439)
(92.68412967972316, -92.9078942326061)
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:
$$x_{1} = 61.2729534415634$$
$$x_{2} = 36.1514414910436$$
$$x_{3} = 5.06267917117524$$
$$x_{4} = 54.9914846404513$$
$$x_{5} = 73.8368718590989$$
$$x_{6} = 42.4303637527494$$
$$x_{7} = 98.9667658004856$$
$$x_{8} = 29.8746827273128$$
$$x_{9} = 23.60213003453$$
$$x_{10} = 17.3393298030427$$
$$x_{11} = 48.7105340009097$$
$$x_{12} = 11.1072905657786$$
$$x_{13} = 86.4015846605975$$
$$x_{14} = 80.1191545145906$$
$$x_{15} = 67.5547826177155$$
$$x_{16} = 92.6841296797232$$
Puntos máximos de la función:
$$x_{16} = 64.4138302477556$$
$$x_{16} = 58.1321658716346$$
$$x_{16} = 89.5428444653399$$
$$x_{16} = 83.2603534390183$$
$$x_{16} = 20.4688629160207$$
$$x_{16} = 45.5703287126706$$
$$x_{16} = 8.03139099623953$$
$$x_{16} = 14.2164990994671$$
$$x_{16} = 95.8254375766894$$
$$x_{16} = 33.0127041187522$$
$$x_{16} = 2.49249324020916$$
$$x_{16} = 39.2907044598106$$
$$x_{16} = 26.7376687721596$$
$$x_{16} = 51.8509314096671$$
$$x_{16} = 70.6957994975412$$
$$x_{16} = 76.9779922603215$$
Decrece en los intervalos
$$\left[98.9667658004856, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, 5.06267917117524\right]$$