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$$- \frac{x^{2} \left(8 \tan^{2}{\left(4 x \right)} + 8\right) \sin{\left(3 x \right)}}{\tan^{3}{\left(4 x \right)}} + \frac{3 x^{2} \cos{\left(3 x \right)} + 2 x \sin{\left(3 x \right)}}{\tan^{2}{\left(4 x \right)}} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -8.24668071567321$$
$$x_{2} = -34.164820107789$$
$$x_{3} = -82.0741080750334$$
$$x_{4} = -79.717913584841$$
$$x_{5} = 58.5121631731099$$
$$x_{6} = 36.5210145979813$$
$$x_{7} = -86.0010988920206$$
$$x_{8} = -31.8086256175967$$
$$x_{9} = -12.1736715326604$$
$$x_{10} = -1.96349540849362$$
$$x_{11} = -21.5984494934298$$
$$x_{12} = 12.1736715326604$$
$$x_{13} = -13.7444678594553$$
$$x_{14} = 26.2210073022975$$
$$x_{15} = -43.5895980685584$$
$$x_{16} = -3.53429173528852$$
$$x_{17} = -96.2112750161874$$
$$x_{18} = 40.4480054149686$$
$$x_{19} = 1.96349540849362$$
$$x_{20} = -87.5718952188155$$
$$x_{21} = -57.7267650097125$$
$$x_{22} = 70.2931356240716$$
$$x_{23} = -65.5807466436869$$
$$x_{24} = 18.45685683984$$
$$x_{25} = 14.5298660228528$$
$$x_{26} = -39.7525927982518$$
$$x_{27} = 92.2842841992002$$
$$x_{28} = 97.7820713429823$$
$$x_{29} = 5.89048622548086$$
$$x_{30} = 74.2201264410589$$
$$x_{31} = 53.7997741927252$$
$$x_{32} = 93.8550805259951$$
$$x_{33} = 90.0180410537606$$
$$x_{34} = 80.5033117482384$$
$$x_{35} = 23.9546439836222$$
$$x_{36} = -42.0188017417635$$
$$x_{37} = 49.872783375738$$
$$x_{38} = 30.2378292908018$$
$$x_{39} = 66.3661448070844$$
$$x_{40} = -100.138265833175$$
$$x_{41} = 60.0829594999048$$
$$x_{42} = -52.2289778659303$$
$$x_{43} = -5.89048622548086$$
$$x_{44} = -64.009950316892$$
$$x_{45} = 56.1559686829176$$
$$x_{46} = 52.2289778659303$$
$$x_{47} = 62.4391539900971$$
$$x_{48} = 20.0276531666349$$
$$x_{49} = 22.3838476568273$$
$$x_{50} = -97.7820713429823$$
$$x_{51} = -25.5254403104171$$
$$x_{52} = -20.0276531666349$$
$$x_{53} = 44.3749962319558$$
$$x_{54} = 71.8639319508665$$
$$x_{55} = -83.734857777162$$
$$x_{56} = -47.5165888855456$$
$$x_{57} = 27.8816348006094$$
$$x_{58} = -56.1559686829176$$
$$x_{59} = -16.1006623496477$$
$$x_{60} = -38.0918109247762$$
$$x_{61} = -78.1471172580461$$
$$x_{62} = 16.1006623496477$$
$$x_{63} = -53.7997741927252$$
$$x_{64} = -71.8639319508665$$
$$x_{65} = 64.009950316892$$
$$x_{66} = -90.0180410537606$$
$$x_{67} = 42.0188017417635$$
$$x_{68} = 68.0269012258938$$
$$x_{69} = -74.2201264410589$$
$$x_{70} = 8.24668071567321$$
$$x_{71} = -69.5077374606742$$
$$x_{72} = -27.8816348006094$$
$$x_{73} = 46.0357697487582$$
$$x_{74} = 75.7909227678538$$
$$x_{75} = 86.0010988920206$$
$$x_{76} = 31.8086256175967$$
$$x_{77} = -49.872783375738$$
$$x_{78} = -61.7437195617516$$
$$x_{79} = -30.2378292908018$$
$$x_{80} = 9.8174770424681$$
$$x_{81} = -35.7356164345839$$
$$x_{82} = -60.0829594999048$$
$$x_{83} = 82.0741080750334$$
$$x_{84} = 48.2121133804987$$
$$x_{85} = 84.4303025652257$$
$$x_{86} = 88.3572933822129$$
$$x_{87} = 4.23034666555523$$
$$x_{88} = -93.8550805259951$$
$$x_{89} = -75.7909227678538$$
$$x_{90} = -9.8174770424681$$
$$x_{91} = 34.164820107789$$
$$x_{92} = 100.138265833175$$
$$x_{93} = 78.1471172580461$$
$$x_{94} = -17.7615199396124$$
$$x_{95} = -23.9546439836222$$
$$x_{96} = 38.0918109247762$$
$$x_{97} = 96.2112750161874$$
$$x_{98} = -91.4988860358027$$
$$x_{99} = -68.0269012258938$$
Signos de extremos en los puntos:
(-8.246680715673207, 6.2608969426144e-30)
(-34.164820107789, -2.17721097546631e-25)
(-82.07410807503335, -6.59609845351441e-25)
(-79.717913584841, -4.90825406692673e-25)
(58.5121631731099, -7.07266357608159e-26)
(36.52101459798135, 5.40724256083413e-26)
(-86.0010988920206, -4.95822701002057e-25)
(-31.808625617596658, -1.4378464424251e-26)
(-12.17367153266045, 1.61163436116136e-27)
(-1.9634954084936207, 1.38293306821013e-31)
(-21.59844949342983, -1.65784884322066e-27)
(12.17367153266045, -1.61163436116136e-27)
(-13.744467859455346, 7.33787534168653e-28)
(26.221007302297515, -11.9221635608809)
(-43.58959806855838, 3.78152552331241e-27)
(-3.5342917352885173, 3.50482927059889e-30)
(-96.21127501618741, 6.19612491365836e-25)
(40.44800541496859, 2.64682856028215e-25)
(1.9634954084936207, -1.38293306821013e-31)
(-87.57189521881548, 4.91123445361707e-25)
(-57.72676500971245, 1.50324135592178e-26)
(70.29313562407162, -4.10777690887924e-27)
(-65.58074664368694, -3.44708611806669e-25)
(18.456856839840036, -1.8909097567018e-27)
(14.529866022852794, -1.93377673853829e-29)
(-39.75259279825185, 27.4023700150795)
(92.28428419920017, 8.51722226166116e-25)
(97.78207134298232, -4.29746709201086e-24)
(5.8904862254808625, -2.35918695723909e-29)
(74.22012644105887, 4.10777448404942e-26)
(53.79977419272521, -6.49812972406622e-28)
(93.85508052599508, -2.97396843044389e-24)
(90.0180410537606, -140.513114545074)
(80.50331174823845, 1.54845939759556e-24)
(23.954643983622173, 8.4257067990377e-28)
(-42.01880174176348, -4.68631066006037e-26)
(49.87278337573797, -1.37646597341335e-26)
(30.23782929080176, 3.02135757392926e-27)
(66.36614480708438, -8.75107808780236e-27)
(-100.13826583317466, 9.80029047486156e-25)
(60.082959499904796, -7.90231894133868e-28)
(-52.22897786593031, 4.23259460797179e-26)
(-5.8904862254808625, 2.35918695723909e-29)
(-64.00995031689203, 1.05733941246782e-24)
(56.15596868291755, -3.42195627958829e-26)
(52.22897786593031, -4.23259460797179e-26)
(62.43915399009714, -6.99503911072116e-26)
(20.02765316663493, -3.6842680287519e-27)
(22.383847656827278, -1.34558340972988e-26)
(-97.78207134298232, 4.29746709201086e-24)
(-25.52544031041707, -1.44627911109129e-26)
(-20.02765316663493, 3.6842680287519e-27)
(44.374996231955826, 2.72926309421717e-25)
(71.86393195086652, 1.92522074360381e-24)
(-83.73485777716203, 121.582284248689)
(-47.51658888554562, 4.5239454973069e-27)
(27.881634800609415, 6.91987492250535e-28)
(-56.15596868291755, 3.42195627958829e-26)
(-16.100662349647692, 9.72194701602062e-27)
(-38.09181092477624, -1.70223332931575e-25)
(-78.14711725804611, -3.05189764898648e-25)
(16.100662349647692, -9.72194701602062e-27)
(-53.79977419272521, 6.49812972406622e-28)
(-71.86393195086652, -1.92522074360381e-24)
(64.00995031689203, -1.05733941246782e-24)
(-90.0180410537606, 140.513114545074)
(42.01880174176348, 4.68631066006037e-26)
(68.02690122589381, 80.245192545902)
(-74.22012644105887, -4.10777448404942e-26)
(8.246680715673207, -6.2608969426144e-30)
(-69.50773746067418, -6.70307204277905e-25)
(-27.881634800609415, -6.91987492250535e-28)
(46.035769748758234, -36.7492258519543)
(75.79092276785376, 1.56034839993081e-24)
(86.0010988920206, 4.95822701002057e-25)
(31.808625617596658, 1.4378464424251e-26)
(-49.87278337573797, 1.37646597341335e-26)
(-61.74371956175159, -66.1063494799021)
(-30.23782929080176, -3.02135757392926e-27)
(9.817477042468104, -5.36894730252294e-30)
(-35.735616434583896, -2.63900119646912e-26)
(-60.082959499904796, 7.90231894133868e-28)
(82.07410807503335, 6.59609845351441e-25)
(48.21211338049869, 40.3060053222755)
(84.43030256522569, 3.20111068612285e-24)
(88.35729338221293, 2.63302798971338e-24)
(4.23034666555523, 0.310277282604834)
(-93.85508052599508, 2.97396843044389e-24)
(-75.79092276785376, -1.56034839993081e-24)
(-9.817477042468104, 5.36894730252294e-30)
(34.164820107789, 2.17721097546631e-25)
(100.13826583317466, -9.80029047486156e-25)
(78.14711725804611, 3.05189764898648e-25)
(-17.761519939612445, -5.47034583693541)
(-23.954643983622173, -8.4257067990377e-28)
(38.09181092477624, 1.70223332931575e-25)
(96.21127501618741, -6.19612491365836e-25)
(-91.49888603580273, 2.24323612628549e-25)
(-68.02690122589381, -80.245192545902)
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:
$$x_{1} = -8.24668071567321$$
$$x_{2} = 36.5210145979813$$
$$x_{3} = -12.1736715326604$$
$$x_{4} = -1.96349540849362$$
$$x_{5} = -13.7444678594553$$
$$x_{6} = 26.2210073022975$$
$$x_{7} = -43.5895980685584$$
$$x_{8} = -3.53429173528852$$
$$x_{9} = -96.2112750161874$$
$$x_{10} = 40.4480054149686$$
$$x_{11} = -87.5718952188155$$
$$x_{12} = -57.7267650097125$$
$$x_{13} = 92.2842841992002$$
$$x_{14} = 74.2201264410589$$
$$x_{15} = 90.0180410537606$$
$$x_{16} = 80.5033117482384$$
$$x_{17} = 23.9546439836222$$
$$x_{18} = 30.2378292908018$$
$$x_{19} = -100.138265833175$$
$$x_{20} = -52.2289778659303$$
$$x_{21} = -5.89048622548086$$
$$x_{22} = -64.009950316892$$
$$x_{23} = -97.7820713429823$$
$$x_{24} = -20.0276531666349$$
$$x_{25} = 44.3749962319558$$
$$x_{26} = 71.8639319508665$$
$$x_{27} = -47.5165888855456$$
$$x_{28} = 27.8816348006094$$
$$x_{29} = -56.1559686829176$$
$$x_{30} = -16.1006623496477$$
$$x_{31} = -53.7997741927252$$
$$x_{32} = 42.0188017417635$$
$$x_{33} = 46.0357697487582$$
$$x_{34} = 75.7909227678538$$
$$x_{35} = 86.0010988920206$$
$$x_{36} = 31.8086256175967$$
$$x_{37} = -49.872783375738$$
$$x_{38} = -61.7437195617516$$
$$x_{39} = -60.0829594999048$$
$$x_{40} = 82.0741080750334$$
$$x_{41} = 84.4303025652257$$
$$x_{42} = 88.3572933822129$$
$$x_{43} = -93.8550805259951$$
$$x_{44} = -9.8174770424681$$
$$x_{45} = 34.164820107789$$
$$x_{46} = 78.1471172580461$$
$$x_{47} = -17.7615199396124$$
$$x_{48} = 38.0918109247762$$
$$x_{49} = -91.4988860358027$$
$$x_{50} = -68.0269012258938$$
Puntos máximos de la función:
$$x_{50} = -34.164820107789$$
$$x_{50} = -82.0741080750334$$
$$x_{50} = -79.717913584841$$
$$x_{50} = 58.5121631731099$$
$$x_{50} = -86.0010988920206$$
$$x_{50} = -31.8086256175967$$
$$x_{50} = -21.5984494934298$$
$$x_{50} = 12.1736715326604$$
$$x_{50} = 1.96349540849362$$
$$x_{50} = 70.2931356240716$$
$$x_{50} = -65.5807466436869$$
$$x_{50} = 18.45685683984$$
$$x_{50} = 14.5298660228528$$
$$x_{50} = -39.7525927982518$$
$$x_{50} = 97.7820713429823$$
$$x_{50} = 5.89048622548086$$
$$x_{50} = 53.7997741927252$$
$$x_{50} = 93.8550805259951$$
$$x_{50} = -42.0188017417635$$
$$x_{50} = 49.872783375738$$
$$x_{50} = 66.3661448070844$$
$$x_{50} = 60.0829594999048$$
$$x_{50} = 56.1559686829176$$
$$x_{50} = 52.2289778659303$$
$$x_{50} = 62.4391539900971$$
$$x_{50} = 20.0276531666349$$
$$x_{50} = 22.3838476568273$$
$$x_{50} = -25.5254403104171$$
$$x_{50} = -83.734857777162$$
$$x_{50} = -38.0918109247762$$
$$x_{50} = -78.1471172580461$$
$$x_{50} = 16.1006623496477$$
$$x_{50} = -71.8639319508665$$
$$x_{50} = 64.009950316892$$
$$x_{50} = -90.0180410537606$$
$$x_{50} = 68.0269012258938$$
$$x_{50} = -74.2201264410589$$
$$x_{50} = 8.24668071567321$$
$$x_{50} = -69.5077374606742$$
$$x_{50} = -27.8816348006094$$
$$x_{50} = -30.2378292908018$$
$$x_{50} = 9.8174770424681$$
$$x_{50} = -35.7356164345839$$
$$x_{50} = 48.2121133804987$$
$$x_{50} = 4.23034666555523$$
$$x_{50} = -75.7909227678538$$
$$x_{50} = 100.138265833175$$
$$x_{50} = -23.9546439836222$$
$$x_{50} = 96.2112750161874$$
Decrece en los intervalos
$$\left[92.2842841992002, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -100.138265833175\right]$$