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$$\frac{1}{x \sin{\left(2 x \right)}} \sin{\left(x \right)} + \frac{\left(1 - \cos{\left(x \right)}\right) \left(- 2 x \cos{\left(2 x \right)} - \sin{\left(2 x \right)}\right)}{x^{2} \sin^{2}{\left(2 x \right)}} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -21.0997786190612$$
$$x_{2} = -2.35903204498278$$
$$x_{3} = -14.8222285221178$$
$$x_{4} = -92.0137428813551$$
$$x_{5} = 46.2253307504569$$
$$x_{6} = 85.7307769850148$$
$$x_{7} = -83.9217438912508$$
$$x_{8} = -33.6612081744243$$
$$x_{9} = -27.3799241503631$$
$$x_{10} = -48.0341830943912$$
$$x_{11} = 60.5993672152362$$
$$x_{12} = 22.9076920601837$$
$$x_{13} = 29.1883117520455$$
$$x_{14} = 4.11067205558904$$
$$x_{15} = 92.0137428813551$$
$$x_{16} = -39.9430921063837$$
$$x_{17} = -60.5993672152362$$
$$x_{18} = -90.204699041177$$
$$x_{19} = 27.3799241503631$$
$$x_{20} = -35.469835821083$$
$$x_{21} = 96.4876842084868$$
$$x_{22} = 41.7518578220228$$
$$x_{23} = 83.9217438912508$$
$$x_{24} = 10.3556266699783$$
$$x_{25} = -4.11067205558904$$
$$x_{26} = 16.628990050393$$
$$x_{27} = 33.6612081744243$$
$$x_{28} = 2.35903204498278$$
$$x_{29} = 14.8222285221178$$
$$x_{30} = 8.55304201163282$$
$$x_{31} = 66.8821260674787$$
$$x_{32} = -41.7518578220228$$
$$x_{33} = 90.204699041177$$
$$x_{34} = -71.3559554197142$$
$$x_{35} = -96.4876842084868$$
$$x_{36} = 35.469835821083$$
$$x_{37} = 52.507796494609$$
$$x_{38} = 77.6388260588097$$
$$x_{39} = 410.644754035796$$
$$x_{40} = 58.7904163791633$$
$$x_{41} = 48.0341830943912$$
$$x_{42} = -77.6388260588097$$
$$x_{43} = -85.7307769850148$$
$$x_{44} = -79.447845725128$$
$$x_{45} = -52.507796494609$$
$$x_{46} = -16.628990050393$$
$$x_{47} = -146.752183087622$$
$$x_{48} = 54.3167067346688$$
$$x_{49} = -65.0731456714068$$
$$x_{50} = -8.55304201163282$$
$$x_{51} = -54.3167067346688$$
$$x_{52} = 71.3559554197142$$
$$x_{53} = -10.3556266699783$$
$$x_{54} = -98.2967367830456$$
$$x_{55} = -46.2253307504569$$
$$x_{56} = 39.9430921063837$$
$$x_{57} = 98.2967367830456$$
Signos de extremos en los puntos:
(-21.09977861906122, -0.0789400167897395)
(-2.3590320449827753, -0.724508135686241)
(-14.822228522117832, -0.112409283601198)
(-92.0137428813551, 0.0180964539367232)
(46.22533075045695, -0.0360236141212341)
(85.73077698501483, 0.019422739816553)
(-83.92174389125084, -0.0198414380991413)
(-33.66120817442426, -0.0494723651395544)
(-27.37992415036312, -0.0608257506350598)
(-48.03418309439118, 0.0346668675653127)
(60.59936721523623, 0.0274781383720191)
(22.90769206018372, 0.0727061485455461)
(29.188311752045504, 0.0570558388985918)
(4.11067205558904, 0.408210556939668)
(92.0137428813551, 0.0180964539367232)
(-39.94309210638365, -0.0416903192670335)
(-60.59936721523623, 0.0274781383720191)
(-90.204699041177, -0.0184593895515073)
(27.37992415036312, -0.0608257506350598)
(-35.46983582108299, 0.0469491101063058)
(96.48768420848683, -0.0172573330831066)
(41.75185782202277, 0.0398838951977928)
(83.92174389125084, -0.0198414380991413)
(10.355626669978271, 0.160994549148767)
(-4.11067205558904, 0.408210556939668)
(16.62899005039297, 0.100181523234274)
(33.66120817442426, -0.0494723651395544)
(2.3590320449827753, -0.724508135686241)
(14.822228522117832, -0.112409283601198)
(8.553042011632824, -0.195054444868888)
(66.88212606747874, 0.0248967359111755)
(-41.75185782202277, 0.0398838951977928)
(90.204699041177, -0.0184593895515073)
(-71.3559554197142, -0.0233356927886555)
(-96.48768420848683, -0.0172573330831066)
(35.46983582108299, 0.0469491101063058)
(52.507796494609025, -0.0317129877503068)
(77.63882605880968, -0.0214471765347026)
(410.6447540357962, -0.0040548349571471)
(58.79041637916331, -0.028323700297562)
(48.03418309439118, 0.0346668675653127)
(-77.63882605880968, -0.0214471765347026)
(-85.73077698501483, 0.019422739816553)
(-79.44784572512803, 0.0209588024678898)
(-52.507796494609025, -0.0317129877503068)
(-16.62899005039297, 0.100181523234274)
(-146.75218308762211, -0.0113463800149005)
(54.31670673466879, 0.0306567381010815)
(-65.07314567140679, -0.025588894223446)
(-8.553042011632824, -0.195054444868888)
(-54.31670673466879, 0.0306567381010815)
(71.3559554197142, -0.0233356927886555)
(-10.355626669978271, 0.160994549148767)
(-98.29673678304557, 0.0169397190694041)
(-46.22533075045695, -0.0360236141212341)
(39.94309210638365, -0.0416903192670335)
(98.29673678304557, 0.0169397190694041)
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:
$$x_{1} = -92.0137428813551$$
$$x_{2} = 85.7307769850148$$
$$x_{3} = -48.0341830943912$$
$$x_{4} = 60.5993672152362$$
$$x_{5} = 22.9076920601837$$
$$x_{6} = 29.1883117520455$$
$$x_{7} = 4.11067205558904$$
$$x_{8} = 92.0137428813551$$
$$x_{9} = -60.5993672152362$$
$$x_{10} = -35.469835821083$$
$$x_{11} = 41.7518578220228$$
$$x_{12} = 10.3556266699783$$
$$x_{13} = -4.11067205558904$$
$$x_{14} = 16.628990050393$$
$$x_{15} = 66.8821260674787$$
$$x_{16} = -41.7518578220228$$
$$x_{17} = 35.469835821083$$
$$x_{18} = 48.0341830943912$$
$$x_{19} = -85.7307769850148$$
$$x_{20} = -79.447845725128$$
$$x_{21} = -16.628990050393$$
$$x_{22} = 54.3167067346688$$
$$x_{23} = -54.3167067346688$$
$$x_{24} = -10.3556266699783$$
$$x_{25} = -98.2967367830456$$
$$x_{26} = 98.2967367830456$$
Puntos máximos de la función:
$$x_{26} = -21.0997786190612$$
$$x_{26} = -2.35903204498278$$
$$x_{26} = -14.8222285221178$$
$$x_{26} = 46.2253307504569$$
$$x_{26} = -83.9217438912508$$
$$x_{26} = -33.6612081744243$$
$$x_{26} = -27.3799241503631$$
$$x_{26} = -39.9430921063837$$
$$x_{26} = -90.204699041177$$
$$x_{26} = 27.3799241503631$$
$$x_{26} = 96.4876842084868$$
$$x_{26} = 83.9217438912508$$
$$x_{26} = 33.6612081744243$$
$$x_{26} = 2.35903204498278$$
$$x_{26} = 14.8222285221178$$
$$x_{26} = 8.55304201163282$$
$$x_{26} = 90.204699041177$$
$$x_{26} = -71.3559554197142$$
$$x_{26} = -96.4876842084868$$
$$x_{26} = 52.507796494609$$
$$x_{26} = 77.6388260588097$$
$$x_{26} = 410.644754035796$$
$$x_{26} = 58.7904163791633$$
$$x_{26} = -77.6388260588097$$
$$x_{26} = -52.507796494609$$
$$x_{26} = -146.752183087622$$
$$x_{26} = -65.0731456714068$$
$$x_{26} = -8.55304201163282$$
$$x_{26} = 71.3559554197142$$
$$x_{26} = -46.2253307504569$$
$$x_{26} = 39.9430921063837$$
Decrece en los intervalos
$$\left[98.2967367830456, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -98.2967367830456\right]$$