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$$- \frac{\sin{\left(x \right)} \operatorname{atan}{\left(7 x \right)}}{5} + \frac{7 \cos{\left(x \right)}}{5 \left(49 x^{2} + 1\right)} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 40.8407591425359$$
$$x_{2} = 100.530973921756$$
$$x_{3} = -28.2744480075961$$
$$x_{4} = 69.1150574426549$$
$$x_{5} = 3.15100482407892$$
$$x_{6} = 62.8318761418628$$
$$x_{7} = 84.823014300677$$
$$x_{8} = -34.5575955435353$$
$$x_{9} = -59.69028598254$$
$$x_{10} = -50.2655185173536$$
$$x_{11} = -72.256648473579$$
$$x_{12} = 50.2655185173536$$
$$x_{13} = -47.1239308369192$$
$$x_{14} = 97.3893818589064$$
$$x_{15} = -65.9734666491843$$
$$x_{16} = 87.964606066119$$
$$x_{17} = 37.6991759878229$$
$$x_{18} = -18.8498131052308$$
$$x_{19} = 25.1328857253434$$
$$x_{20} = 34.5575955435353$$
$$x_{21} = 21.9913374004364$$
$$x_{22} = -78.5398311003412$$
$$x_{23} = -84.823014300677$$
$$x_{24} = 43.9823442609731$$
$$x_{25} = 12.5669506041308$$
$$x_{26} = -53.4071070500068$$
$$x_{27} = 18.8498131052308$$
$$x_{28} = -125.663711906957$$
$$x_{29} = -6.28551985758014$$
$$x_{30} = -43.9823442609731$$
$$x_{31} = -91.1061979218887$$
$$x_{32} = -9.42581132885092$$
$$x_{33} = 91.1061979218887$$
$$x_{34} = -75.3982397031955$$
$$x_{35} = 72.256648473579$$
$$x_{36} = -37.6991759878229$$
$$x_{37} = -94.2477898561398$$
$$x_{38} = -97.3893818589064$$
$$x_{39} = 56.548696250726$$
$$x_{40} = 65.9734666491843$$
$$x_{41} = 31.4160189482124$$
$$x_{42} = -81.6814226397312$$
$$x_{43} = 15.7083339551082$$
$$x_{44} = 9.42581132885092$$
$$x_{45} = 47.1239308369192$$
$$x_{46} = 28.2744480075961$$
$$x_{47} = -21.9913374004364$$
$$x_{48} = 78.5398311003412$$
$$x_{49} = -69.1150574426549$$
$$x_{50} = -62.8318761418628$$
$$x_{51} = 81.6814226397312$$
$$x_{52} = -25.1328857253434$$
$$x_{53} = -40.8407591425359$$
$$x_{54} = 53.4071070500068$$
$$x_{55} = -15.7083339551082$$
$$x_{56} = 0.456935759159445$$
$$x_{57} = 75.3982397031955$$
$$x_{58} = -1448.27421334826$$
$$x_{59} = 94.2477898561398$$
$$x_{60} = -3.15100482407892$$
$$x_{61} = -12.5669506041308$$
$$x_{62} = -56.548696250726$$
$$x_{63} = -100.530973921756$$
$$x_{64} = -31.4160189482124$$
$$x_{65} = 6.28551985758014$$
$$x_{66} = -87.964606066119$$
$$x_{67} = 59.69028598254$$
Signos de extremos en los puntos:
(40.840759142535944, -0.313459686512763)
(100.53097392175573, 0.313875060307489)
(-28.274448007596067, 0.313148768421786)
(69.1150574426549, 0.313745876542117)
(3.1510048240789175, -0.305084553805719)
(62.83187614186276, 0.313704537817189)
(84.82301430067703, -0.313822429844181)
(-34.557595543535314, 0.313332492056769)
(-59.69028598254, 0.313680604892405)
(-50.265518517353634, -0.313590856582214)
(-72.25664847357905, 0.313763849914225)
(50.265518517353634, 0.313590856582214)
(-47.12393083691916, 0.313552962935163)
(97.38938185890642, -0.313865892416862)
(-65.97346664918427, 0.313726191429446)
(87.96460606611903, 0.313834459659947)
(37.69917598782292, 0.313401388949929)
(-18.849813105230847, -0.312643543356069)
(25.13288572534344, 0.313022459847738)
(34.557595543535314, -0.313332492056769)
(21.991337400436436, -0.312860065186453)
(-78.53983110034122, 0.313795483067281)
(-84.82301430067703, 0.313822429844181)
(43.98234426097308, 0.313509655978696)
(12.566950604130808, 0.311885773715038)
(-53.40710705000676, 0.313624292196214)
(18.849813105230847, 0.312643543356069)
(-125.66371190695742, -0.313931901257722)
(-6.285519857580139, -0.309613608941595)
(-43.98234426097308, -0.313509655978696)
(-91.10619792188866, 0.313845659835682)
(-9.42581132885092, 0.311128140924491)
(91.10619792188866, -0.313845659835682)
(-75.39823970319554, -0.313780325511985)
(72.25664847357905, -0.313763849914225)
(-37.69917598782292, -0.313401388949929)
(-94.24778985613978, -0.313856113335073)
(-97.38938185890642, 0.313865892416862)
(56.54869625072598, 0.31365401277349)
(65.97346664918427, -0.313726191429446)
(31.416018948212397, 0.313249816147344)
(-81.68142263973122, -0.313809474661132)
(15.708333955108206, -0.312340423329518)
(9.42581132885092, -0.311128140924491)
(47.12393083691916, -0.313552962935163)
(28.274448007596067, -0.313148768421786)
(-21.991337400436436, 0.312860065186453)
(78.53983110034122, -0.313795483067281)
(-69.1150574426549, -0.313745876542117)
(-62.83187614186276, -0.313704537817189)
(81.68142263973122, 0.313809474661132)
(-25.13288572534344, -0.313022459847738)
(-40.840759142535944, 0.313459686512763)
(53.40710705000676, -0.313624292196214)
(-15.708333955108206, 0.312340423329518)
(0.4569357591594449, 0.227543784365642)
(75.39823970319554, 0.313780325511985)
(-1448.2742133482566, 0.314139537445428)
(94.24778985613978, 0.313856113335073)
(-3.1510048240789175, 0.305084553805719)
(-12.566950604130808, -0.311885773715038)
(-56.54869625072598, -0.31365401277349)
(-100.53097392175573, -0.313875060307489)
(-31.416018948212397, -0.313249816147344)
(6.285519857580139, 0.309613608941595)
(-87.96460606611903, -0.313834459659947)
(59.69028598254, -0.313680604892405)
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:
$$x_{1} = 40.8407591425359$$
$$x_{2} = 3.15100482407892$$
$$x_{3} = 84.823014300677$$
$$x_{4} = -50.2655185173536$$
$$x_{5} = 97.3893818589064$$
$$x_{6} = -18.8498131052308$$
$$x_{7} = 34.5575955435353$$
$$x_{8} = 21.9913374004364$$
$$x_{9} = -125.663711906957$$
$$x_{10} = -6.28551985758014$$
$$x_{11} = -43.9823442609731$$
$$x_{12} = 91.1061979218887$$
$$x_{13} = -75.3982397031955$$
$$x_{14} = 72.256648473579$$
$$x_{15} = -37.6991759878229$$
$$x_{16} = -94.2477898561398$$
$$x_{17} = 65.9734666491843$$
$$x_{18} = -81.6814226397312$$
$$x_{19} = 15.7083339551082$$
$$x_{20} = 9.42581132885092$$
$$x_{21} = 47.1239308369192$$
$$x_{22} = 28.2744480075961$$
$$x_{23} = 78.5398311003412$$
$$x_{24} = -69.1150574426549$$
$$x_{25} = -62.8318761418628$$
$$x_{26} = -25.1328857253434$$
$$x_{27} = 53.4071070500068$$
$$x_{28} = -12.5669506041308$$
$$x_{29} = -56.548696250726$$
$$x_{30} = -100.530973921756$$
$$x_{31} = -31.4160189482124$$
$$x_{32} = -87.964606066119$$
$$x_{33} = 59.69028598254$$
Puntos máximos de la función:
$$x_{33} = 100.530973921756$$
$$x_{33} = -28.2744480075961$$
$$x_{33} = 69.1150574426549$$
$$x_{33} = 62.8318761418628$$
$$x_{33} = -34.5575955435353$$
$$x_{33} = -59.69028598254$$
$$x_{33} = -72.256648473579$$
$$x_{33} = 50.2655185173536$$
$$x_{33} = -47.1239308369192$$
$$x_{33} = -65.9734666491843$$
$$x_{33} = 87.964606066119$$
$$x_{33} = 37.6991759878229$$
$$x_{33} = 25.1328857253434$$
$$x_{33} = -78.5398311003412$$
$$x_{33} = -84.823014300677$$
$$x_{33} = 43.9823442609731$$
$$x_{33} = 12.5669506041308$$
$$x_{33} = -53.4071070500068$$
$$x_{33} = 18.8498131052308$$
$$x_{33} = -91.1061979218887$$
$$x_{33} = -9.42581132885092$$
$$x_{33} = -97.3893818589064$$
$$x_{33} = 56.548696250726$$
$$x_{33} = 31.4160189482124$$
$$x_{33} = -21.9913374004364$$
$$x_{33} = 81.6814226397312$$
$$x_{33} = -40.8407591425359$$
$$x_{33} = -15.7083339551082$$
$$x_{33} = 0.456935759159445$$
$$x_{33} = 75.3982397031955$$
$$x_{33} = -1448.27421334826$$
$$x_{33} = 94.2477898561398$$
$$x_{33} = -3.15100482407892$$
$$x_{33} = 6.28551985758014$$
Decrece en los intervalos
$$\left[97.3893818589064, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -125.663711906957\right]$$