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$$\frac{2 \sin{\left(2 x \right)}}{x^{7}} - \frac{7 \left(1 - \cos{\left(2 x \right)}\right)}{x^{8}} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -102.067483634462$$
$$x_{2} = -36.031482040422$$
$$x_{3} = 26.5725766811847$$
$$x_{4} = -13.890331420736$$
$$x_{5} = -45.4762817024291$$
$$x_{6} = -39.1808152146506$$
$$x_{7} = -51.7687731884345$$
$$x_{8} = -29.7279353375132$$
$$x_{9} = -78.5398163397448$$
$$x_{10} = -53.4070751110265$$
$$x_{11} = -42.329002868703$$
$$x_{12} = -9.42477796076938$$
$$x_{13} = 28.2743338823081$$
$$x_{14} = 50.2654824574367$$
$$x_{15} = -97.3893722612836$$
$$x_{16} = 51.7687731884345$$
$$x_{17} = -100.530964914873$$
$$x_{18} = 34.5575191894877$$
$$x_{19} = 65.9734457253857$$
$$x_{20} = 3.14159265358979$$
$$x_{21} = -17.0766005112267$$
$$x_{22} = 42.329002868703$$
$$x_{23} = 78.5398163397448$$
$$x_{24} = 59.6902604182061$$
$$x_{25} = 100.530964914873$$
$$x_{26} = -72.2566310325652$$
$$x_{27} = 21.9911485751286$$
$$x_{28} = 10.6788567234762$$
$$x_{29} = 20.2491969875335$$
$$x_{30} = -37.6991118430775$$
$$x_{31} = -81.6814089933346$$
$$x_{32} = -20.2491969875335$$
$$x_{33} = -21.9911485751286$$
$$x_{34} = 12.5663706143592$$
$$x_{35} = -87.9645943005142$$
$$x_{36} = -3.14159265358979$$
$$x_{37} = -73.7800245819846$$
$$x_{38} = -7.41285916300953$$
$$x_{39} = -94.2477796076938$$
$$x_{40} = 15.707963267949$$
$$x_{41} = 18.8495559215388$$
$$x_{42} = 40.8407044966673$$
$$x_{43} = 92.639220267433$$
$$x_{44} = 102.067483634462$$
$$x_{45} = -43.9822971502571$$
$$x_{46} = -6.28318530717959$$
$$x_{47} = -89.4963027856114$$
$$x_{48} = 95.7820508924394$$
$$x_{49} = -28.2743338823081$$
$$x_{50} = -3.99264704614295$$
$$x_{51} = -34.5575191894877$$
$$x_{52} = 64.3483114598181$$
$$x_{53} = 81.6814089933346$$
$$x_{54} = -75.398223686155$$
$$x_{55} = 94.2477796076938$$
$$x_{56} = 48.6228274209788$$
$$x_{57} = 58.0592537158123$$
$$x_{58} = -59.6902604182061$$
$$x_{59} = 87.9645943005142$$
$$x_{60} = 39.1808152146506$$
$$x_{61} = -56.5486677646163$$
$$x_{62} = 13.890331420736$$
$$x_{63} = -95.7820508924394$$
$$x_{64} = 80.066927048268$$
$$x_{65} = 29.7279353375132$$
$$x_{66} = 47.1238898038469$$
$$x_{67} = -15.707963267949$$
$$x_{68} = -12.5663706143592$$
$$x_{69} = -67.4924307958541$$
$$x_{70} = 73.7800245819846$$
$$x_{71} = -64.3483114598181$$
$$x_{72} = 6.28318530717959$$
$$x_{73} = -58.0592537158123$$
$$x_{74} = 70.636325620644$$
$$x_{75} = 3.99264704614295$$
$$x_{76} = -50.2654824574367$$
$$x_{77} = 37.6991118430775$$
$$x_{78} = 36.031482040422$$
$$x_{79} = 43.9822971502571$$
$$x_{80} = 56.5486677646163$$
$$x_{81} = -65.9734457253857$$
$$x_{82} = 54.9142217653629$$
$$x_{83} = 89.4963027856114$$
$$x_{84} = 86.3532889745075$$
$$x_{85} = -31.4159265358979$$
$$x_{86} = -23.4135576431408$$
$$x_{87} = 67.4924307958541$$
$$x_{88} = -86.3532889745075$$
$$x_{89} = 72.2566310325652$$
$$x_{90} = -80.066927048268$$
Signos de extremos en los puntos:
(-102.06748363446222, -1.73104263558768e-14)
(-36.03148204042201, -2.51290734825533e-11)
(26.57257668118469, 2.10147606245822e-10)
(-13.890331420736025, -1.88498543002384e-8)
(-45.476281702429105, -4.94277085324328e-12)
(-39.18081521465061, -1.3997933117997e-11)
(-51.76877318843454, -1.99790252499787e-12)
(-29.727935337513163, -9.61386855804499e-11)
(-78.53981633974483, 0)
(-53.40707511102649, 0)
(-42.32900286870297, -8.15839258964748e-12)
(-9.42477796076938, 0)
(28.274333882308138, 0)
(50.26548245743669, 0)
(-97.3893722612836, 0)
(51.76877318843454, 1.99790252499787e-12)
(-100.53096491487338, 0)
(34.55751918948773, 0)
(65.97344572538566, 0)
(3.141592653589793, 0)
(-17.07660051122672, -4.53261635346902e-9)
(42.32900286870297, 8.15839258964748e-12)
(78.53981633974483, 0)
(59.69026041820607, 0)
(100.53096491487338, 0)
(-72.25663103256524, 0)
(21.991148575128552, 0)
(10.678856723476205, 1.14036578210809e-7)
(20.249196987533473, 1.39120291284387e-9)
(-37.69911184307752, 0)
(-81.68140899333463, 0)
(-20.249196987533473, -1.39120291284387e-9)
(-21.991148575128552, 0)
(12.566370614359172, 0)
(-87.96459430051421, 0)
(-3.141592653589793, 0)
(-73.78002458198462, -1.67680357422973e-13)
(-7.412859163009532, -1.32962407180023e-6)
(-94.2477796076938, 0)
(15.707963267948966, 0)
(18.84955592153876, 0)
(40.840704496667314, 0)
(92.63922026743305, 3.41072172792618e-14)
(102.06748363446222, 1.73104263558768e-14)
(-43.982297150257104, 0)
(-6.283185307179586, 0)
(-89.49630278561138, -4.34240798935016e-14)
(95.78205089243944, 2.70060806392863e-14)
(-28.274333882308138, 0)
(-3.992647046142946, -6.99216011839942e-5)
(-34.55751918948773, 0)
(64.3483114598181, 4.36502740429642e-13)
(81.68140899333463, 0)
(-75.39822368615503, 0)
(94.2477796076938, 0)
(48.622827420978844, 3.09673499091551e-12)
(58.05925371581234, 8.9609582936568e-13)
(-59.69026041820607, 0)
(87.96459430051421, 0)
(39.18081521465061, 1.3997933117997e-11)
(-56.548667764616276, 0)
(13.890331420736025, 1.88498543002384e-8)
(-95.78205089243944, -2.70060806392863e-14)
(80.06692704826798, 9.46299879962671e-14)
(29.727935337513163, 9.61386855804499e-11)
(47.1238898038469, 0)
(-15.707963267948966, 0)
(-12.566370614359172, 0)
(-67.49243079585412, -3.12664202973307e-13)
(73.78002458198462, 1.67680357422973e-13)
(-64.3483114598181, -4.36502740429642e-13)
(6.283185307179586, 0)
(-58.05925371581234, -8.9609582936568e-13)
(70.63632562064403, 2.27388418124641e-13)
(3.992647046142946, 6.99216011839942e-5)
(-50.26548245743669, 0)
(37.69911184307752, 0)
(36.03148204042201, 2.51290734825533e-11)
(43.982297150257104, 0)
(56.548667764616276, 0)
(-65.97344572538566, 0)
(54.91422176536288, 1.32274316116306e-12)
(89.49630278561138, 4.34240798935016e-14)
(86.35328897450749, 5.57654163318878e-14)
(-31.41592653589793, 0)
(-23.413557643140777, -5.07177757438681e-10)
(67.49243079585412, 3.12664202973307e-13)
(-86.35328897450749, -5.57654163318878e-14)
(72.25663103256524, 0)
(-80.06692704826798, -9.46299879962671e-14)
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:
$$x_{1} = -102.067483634462$$
$$x_{2} = -36.031482040422$$
$$x_{3} = -13.890331420736$$
$$x_{4} = -45.4762817024291$$
$$x_{5} = -39.1808152146506$$
$$x_{6} = -51.7687731884345$$
$$x_{7} = -29.7279353375132$$
$$x_{8} = -42.329002868703$$
$$x_{9} = 28.2743338823081$$
$$x_{10} = 50.2654824574367$$
$$x_{11} = 34.5575191894877$$
$$x_{12} = 65.9734457253857$$
$$x_{13} = 3.14159265358979$$
$$x_{14} = -17.0766005112267$$
$$x_{15} = 78.5398163397448$$
$$x_{16} = 59.6902604182061$$
$$x_{17} = 100.530964914873$$
$$x_{18} = 21.9911485751286$$
$$x_{19} = -20.2491969875335$$
$$x_{20} = 12.5663706143592$$
$$x_{21} = -73.7800245819846$$
$$x_{22} = -7.41285916300953$$
$$x_{23} = 15.707963267949$$
$$x_{24} = 18.8495559215388$$
$$x_{25} = 40.8407044966673$$
$$x_{26} = -89.4963027856114$$
$$x_{27} = -3.99264704614295$$
$$x_{28} = 81.6814089933346$$
$$x_{29} = 94.2477796076938$$
$$x_{30} = 87.9645943005142$$
$$x_{31} = -95.7820508924394$$
$$x_{32} = 47.1238898038469$$
$$x_{33} = -67.4924307958541$$
$$x_{34} = -64.3483114598181$$
$$x_{35} = 6.28318530717959$$
$$x_{36} = -58.0592537158123$$
$$x_{37} = 37.6991118430775$$
$$x_{38} = 43.9822971502571$$
$$x_{39} = 56.5486677646163$$
$$x_{40} = -23.4135576431408$$
$$x_{41} = -86.3532889745075$$
$$x_{42} = 72.2566310325652$$
$$x_{43} = -80.066927048268$$
Puntos máximos de la función:
$$x_{43} = 26.5725766811847$$
$$x_{43} = -78.5398163397448$$
$$x_{43} = -53.4070751110265$$
$$x_{43} = -9.42477796076938$$
$$x_{43} = -97.3893722612836$$
$$x_{43} = 51.7687731884345$$
$$x_{43} = -100.530964914873$$
$$x_{43} = 42.329002868703$$
$$x_{43} = -72.2566310325652$$
$$x_{43} = 10.6788567234762$$
$$x_{43} = 20.2491969875335$$
$$x_{43} = -37.6991118430775$$
$$x_{43} = -81.6814089933346$$
$$x_{43} = -21.9911485751286$$
$$x_{43} = -87.9645943005142$$
$$x_{43} = -3.14159265358979$$
$$x_{43} = -94.2477796076938$$
$$x_{43} = 92.639220267433$$
$$x_{43} = 102.067483634462$$
$$x_{43} = -43.9822971502571$$
$$x_{43} = -6.28318530717959$$
$$x_{43} = 95.7820508924394$$
$$x_{43} = -28.2743338823081$$
$$x_{43} = -34.5575191894877$$
$$x_{43} = 64.3483114598181$$
$$x_{43} = -75.398223686155$$
$$x_{43} = 48.6228274209788$$
$$x_{43} = 58.0592537158123$$
$$x_{43} = -59.6902604182061$$
$$x_{43} = 39.1808152146506$$
$$x_{43} = -56.5486677646163$$
$$x_{43} = 13.890331420736$$
$$x_{43} = 80.066927048268$$
$$x_{43} = 29.7279353375132$$
$$x_{43} = -15.707963267949$$
$$x_{43} = -12.5663706143592$$
$$x_{43} = 73.7800245819846$$
$$x_{43} = 70.636325620644$$
$$x_{43} = 3.99264704614295$$
$$x_{43} = -50.2654824574367$$
$$x_{43} = 36.031482040422$$
$$x_{43} = -65.9734457253857$$
$$x_{43} = 54.9142217653629$$
$$x_{43} = 89.4963027856114$$
$$x_{43} = 86.3532889745075$$
$$x_{43} = -31.4159265358979$$
$$x_{43} = 67.4924307958541$$
Decrece en los intervalos
$$\left[100.530964914873, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -102.067483634462\right]$$