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$$2 \log{\left(x \right)} \cos{\left(2 x \right)} + \frac{\sin{\left(2 x \right)}}{x} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 2.46662246182406$$
$$x_{2} = 8.65276590100135$$
$$x_{3} = 62.0474309910149$$
$$x_{4} = 47.9106365276308$$
$$x_{5} = 52.6228756848429$$
$$x_{6} = 41.6277132716067$$
$$x_{7} = 24.3505588482616$$
$$x_{8} = 96.6045402936603$$
$$x_{9} = 16.4987665379521$$
$$x_{10} = 32.2035605555116$$
$$x_{11} = 99.7461113017511$$
$$x_{12} = 69.901278642307$$
$$x_{13} = 90.321403416883$$
$$x_{14} = 5.524240624726$$
$$x_{15} = 10.2206977223401$$
$$x_{16} = 54.1936286925819$$
$$x_{17} = 55.7643844954788$$
$$x_{18} = 91.8921869333118$$
$$x_{19} = 40.0569975446324$$
$$x_{20} = 60.4766662755471$$
$$x_{21} = 76.1843791520252$$
$$x_{22} = 11.789566393009$$
$$x_{23} = 25.9211023317763$$
$$x_{24} = 33.7742240619455$$
$$x_{25} = 49.4813792496946$$
$$x_{26} = 84.0382748106232$$
$$x_{27} = 38.48628952834$$
$$x_{28} = 44.7691642485154$$
$$x_{29} = 68.3305063083065$$
$$x_{30} = 30.6329132105271$$
$$x_{31} = 3.97248841332099$$
$$x_{32} = 82.4674941961375$$
$$x_{33} = 74.6136025037316$$
$$x_{34} = 63.6181974869599$$
$$x_{35} = 77.755156701807$$
$$x_{36} = 19.6392292115165$$
$$x_{37} = 18.0689381825286$$
$$x_{38} = 46.3398980273589$$
$$x_{39} = 98.1753256022933$$
$$x_{40} = 85.609056077116$$
$$x_{41} = 88.7506204145858$$
$$x_{42} = 66.7597352667801$$
$$x_{43} = 27.491679801302$$
Signos de extremos en los puntos:
(2.4666224618240604, -0.880919839660843)
(8.65276590100135, -2.15710574229964)
(62.047430991014885, -4.12789124294944)
(47.910636527630835, 3.86932346304722)
(52.622875684842924, -3.9631395342942)
(41.62771327160666, 3.72874678453796)
(24.35055884826164, -3.19248877006214)
(96.6045402936603, -4.57062281060288)
(16.49876653795208, 2.80312182745805)
(32.203560555511636, 3.47204230855898)
(99.74611130175111, -4.60262534088608)
(69.90127864230699, 4.24707791803583)
(90.32140341688302, -4.50337105555731)
(5.524240624725996, -1.70675427756413)
(10.220697722340134, 2.32390022754927)
(54.19362869258188, 3.99255268966997)
(55.76438449547882, -4.02112539846379)
(91.89218693331178, 4.5206127341262)
(40.05699754463239, -3.69028226850725)
(60.476666275547075, 4.10224927799845)
(76.18437915202516, 4.33315147348226)
(11.789566393008972, -2.46685050885951)
(25.921102331776293, 3.2550002466069)
(33.774224061945475, -3.51966677633177)
(49.48137924969459, -3.9015833367826)
(84.03827481062316, -4.43126835340099)
(38.486289528339974, 3.65027894293774)
(44.769164248515445, 3.80150319881563)
(68.3305063083065, -4.2243499809984)
(30.632913210527114, -3.42203610033169)
(3.9724884133209946, 1.37368587004475)
(82.46749419613745, 4.41240004044145)
(74.61360250373158, -4.3123176230874)
(63.61819748695992, 4.15289211648199)
(77.75515670180697, -4.35356012395842)
(19.639229211516483, 2.97742021811584)
(18.06893818252863, -2.89406206363672)
(46.33989802735888, -3.83598814383295)
(98.17532560229327, 4.58675208952962)
(85.60905607711597, 4.44978723991936)
(88.75062041458582, 4.48582688119475)
(66.75973526678014, 4.20109345733287)
(27.491679801302, -3.31383349933388)
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:
$$x_{1} = 2.46662246182406$$
$$x_{2} = 8.65276590100135$$
$$x_{3} = 62.0474309910149$$
$$x_{4} = 52.6228756848429$$
$$x_{5} = 24.3505588482616$$
$$x_{6} = 96.6045402936603$$
$$x_{7} = 99.7461113017511$$
$$x_{8} = 90.321403416883$$
$$x_{9} = 5.524240624726$$
$$x_{10} = 55.7643844954788$$
$$x_{11} = 40.0569975446324$$
$$x_{12} = 11.789566393009$$
$$x_{13} = 33.7742240619455$$
$$x_{14} = 49.4813792496946$$
$$x_{15} = 84.0382748106232$$
$$x_{16} = 68.3305063083065$$
$$x_{17} = 30.6329132105271$$
$$x_{18} = 74.6136025037316$$
$$x_{19} = 77.755156701807$$
$$x_{20} = 18.0689381825286$$
$$x_{21} = 46.3398980273589$$
$$x_{22} = 27.491679801302$$
Puntos máximos de la función:
$$x_{22} = 47.9106365276308$$
$$x_{22} = 41.6277132716067$$
$$x_{22} = 16.4987665379521$$
$$x_{22} = 32.2035605555116$$
$$x_{22} = 69.901278642307$$
$$x_{22} = 10.2206977223401$$
$$x_{22} = 54.1936286925819$$
$$x_{22} = 91.8921869333118$$
$$x_{22} = 60.4766662755471$$
$$x_{22} = 76.1843791520252$$
$$x_{22} = 25.9211023317763$$
$$x_{22} = 38.48628952834$$
$$x_{22} = 44.7691642485154$$
$$x_{22} = 3.97248841332099$$
$$x_{22} = 82.4674941961375$$
$$x_{22} = 63.6181974869599$$
$$x_{22} = 19.6392292115165$$
$$x_{22} = 98.1753256022933$$
$$x_{22} = 85.609056077116$$
$$x_{22} = 88.7506204145858$$
$$x_{22} = 66.7597352667801$$
Decrece en los intervalos
$$\left[99.7461113017511, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, 2.46662246182406\right]$$