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$$- 2 x^{2} \sin{\left(2 x \right)} + 2 x \cos{\left(2 x \right)} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -83.2582104451025$$
$$x_{2} = -95.8237936557983$$
$$x_{3} = -6.36114938588332$$
$$x_{4} = -61.2692167254242$$
$$x_{5} = 42.4232846216546$$
$$x_{6} = 64.4104114951368$$
$$x_{7} = -87.9702777935942$$
$$x_{8} = -20.4447888830204$$
$$x_{9} = 51.8459215486945$$
$$x_{10} = -97.3945058407034$$
$$x_{11} = 56.5575074028724$$
$$x_{12} = -81.6875295729143$$
$$x_{13} = -14.1723884348932$$
$$x_{14} = 20.4447888830204$$
$$x_{15} = -59.6986350358615$$
$$x_{16} = 81.6875295729143$$
$$x_{17} = 34.5719777382463$$
$$x_{18} = 54.9869634999497$$
$$x_{19} = -31.4318286143515$$
$$x_{20} = 67.5516432560125$$
$$x_{21} = 22.0138459496239$$
$$x_{22} = -39.2826336922998$$
$$x_{23} = -42.4232846216546$$
$$x_{24} = 43.9936604673443$$
$$x_{25} = -7.91680570747386$$
$$x_{26} = 14.1723884348932$$
$$x_{27} = 0$$
$$x_{28} = 95.8237936557983$$
$$x_{29} = -28.2919993689317$$
$$x_{30} = 92.682377840368$$
$$x_{31} = -29.8618677162152$$
$$x_{32} = 78.5461816776562$$
$$x_{33} = 15.739687460157$$
$$x_{34} = 58.1280649399539$$
$$x_{35} = 23.5831338013883$$
$$x_{36} = 59.6986350358615$$
$$x_{37} = -53.4164344328533$$
$$x_{38} = 28.2919993689317$$
$$x_{39} = 37.7123669872618$$
$$x_{40} = -64.4104114951368$$
$$x_{41} = 73.8341988749761$$
$$x_{42} = -50.275426362712$$
$$x_{43} = 9.47734088326452$$
$$x_{44} = 80.1168532266283$$
$$x_{45} = 100.535938096812$$
$$x_{46} = -73.8341988749761$$
$$x_{47} = -67.5516432560125$$
$$x_{48} = -94.2530842748465$$
$$x_{49} = 26.7222398348818$$
$$x_{50} = -43.9936604673443$$
$$x_{51} = -1.8217985837127$$
$$x_{52} = 65.9810230816998$$
$$x_{53} = -58.1280649399539$$
$$x_{54} = 87.9702777935942$$
$$x_{55} = 12.6059515321053$$
$$x_{56} = -17.3076165276153$$
$$x_{57} = 94.2530842748465$$
$$x_{58} = -51.8459215486945$$
$$x_{59} = 7.91680570747386$$
$$x_{60} = -65.9810230816998$$
$$x_{61} = -80.1168532266283$$
$$x_{62} = 1.8217985837127$$
$$x_{63} = -23.5831338013883$$
$$x_{64} = -89.5409744308928$$
$$x_{65} = 45.5640652755696$$
$$x_{66} = -9.47734088326452$$
$$x_{67} = -36.1421462518412$$
$$x_{68} = 89.5409744308928$$
$$x_{69} = -15.739687460157$$
$$x_{70} = -22.0138459496239$$
$$x_{71} = 86.3995847801759$$
$$x_{72} = -3.28916686636117$$
$$x_{73} = 6.36114938588332$$
$$x_{74} = 29.8618677162152$$
$$x_{75} = -86.3995847801759$$
$$x_{76} = 50.275426362712$$
$$x_{77} = -75.4048541703099$$
$$x_{78} = -37.7123669872618$$
$$x_{79} = 70.6929070794294$$
$$x_{80} = -102.10665792544$$
$$x_{81} = 72.2635497085721$$
$$x_{82} = -45.5640652755696$$
$$x_{83} = -72.2635497085721$$
$$x_{84} = 48.7049505853361$$
$$x_{85} = 36.1421462518412$$
Signos de extremos en los puntos:
(-83.25821044510252, -6931.42966061197)
(-95.8237936557983, -9181.69947142519)
(-6.3611493858833175, 39.9733021363577)
(-61.26921672542418, -3753.41701802048)
(42.423284621654574, -1799.23528635748)
(64.41041149513676, -4148.20119934443)
(-87.9702777935942, 7738.26982353423)
(-20.444788883020422, -417.490287838339)
(51.845921548694534, -2687.4997206991)
(-97.39450584070339, 9485.18980748457)
(56.55750740287244, 3198.25176082867)
(-81.68752957291433, 6672.35254391659)
(-14.172388434893186, -200.358453240761)
(20.444788883020422, -417.490287838339)
(-59.698635035861535, 3563.42713034141)
(81.68752957291433, 6672.35254391659)
(34.5719777382463, 1194.72195826454)
(54.9869634999497, -3023.06627893636)
(-31.431828614351502, 987.460229292167)
(67.55164325601251, -4562.72458875131)
(22.01384594962394, 484.110185984573)
(-39.28263369229977, -1542.62555268556)
(-42.423284621654574, -1799.23528635748)
(43.99366046734435, 1934.94235498677)
(-7.916805707473859, -62.1817173222964)
(14.172388434893186, -200.358453240761)
(0, 0)
(95.8237936557983, -9181.69947142519)
(-28.29199936893172, 799.937696298369)
(92.68237784036805, -8589.52320579581)
(-29.86186771621523, -891.231563638471)
(78.54618167765616, 6169.00271691402)
(15.739687460157024, 247.239269966989)
(58.128064939953894, -3378.37204461992)
(23.58313380138835, -555.664873146794)
(59.698635035861535, 3563.42713034141)
(-53.41643443285332, 2852.815598907)
(28.29199936893172, 799.937696298369)
(37.7123669872618, 1421.72288729931)
(-64.41041149513676, -4148.20119934443)
(73.83419887497614, -5450.98899228756)
(-50.27542636271201, 2527.11864426458)
(9.477340883264521, 89.3241268733139)
(80.11685322662832, -6418.21022935247)
(100.53593809681207, 10106.9748861042)
(-73.83419887497614, -5450.98899228756)
(-67.55164325601251, -4562.72458875131)
(-94.25308427484653, 8883.14393752977)
(26.722239834881776, -713.578626333476)
(-43.99366046734435, 1934.94235498677)
(-1.8217985837127004, -2.90945730293889)
(65.9810230816998, 4352.995493029)
(-58.128064939953894, -3378.37204461992)
(87.9702777935942, 7738.26982353423)
(12.60595153210529, 158.412361548588)
(-17.30761652761529, -299.054838257359)
(94.25308427484653, 8883.14393752977)
(-51.845921548694534, -2687.4997206991)
(7.916805707473859, -62.1817173222964)
(-65.9810230816998, 4352.995493029)
(-80.11685322662832, -6418.21022935247)
(1.8217985837127004, -2.90945730293889)
(-23.58313380138835, -555.664873146794)
(-89.54097443089285, -8017.08614880113)
(45.56406527556965, -2075.58422499242)
(-9.477340883264521, 89.3241268733139)
(-36.14214625184125, -1305.75502258676)
(89.54097443089285, -8017.08614880113)
(-15.739687460157024, 247.239269966989)
(-22.01384594962394, 484.110185984573)
(86.39958478017586, -7464.38830041637)
(-3.2891668663611693, 10.3508105527216)
(6.3611493858833175, 39.9733021363577)
(29.86186771621523, -891.231563638471)
(-86.39958478017586, -7464.38830041637)
(50.27542636271201, 2527.11864426458)
(-75.4048541703099, 5685.39209838875)
(-37.7123669872618, 1421.72288729931)
(70.69290707942938, -4996.98718636604)
(-102.10665792544042, -10425.2696286686)
(72.26354970857213, 5221.5206882831)
(-45.56406527556965, -2075.58422499242)
(-72.26354970857213, 5221.5206882831)
(48.70495058533613, -2371.67236954748)
(36.14214625184125, -1305.75502258676)
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:
$$x_{1} = -83.2582104451025$$
$$x_{2} = -95.8237936557983$$
$$x_{3} = -61.2692167254242$$
$$x_{4} = 42.4232846216546$$
$$x_{5} = 64.4104114951368$$
$$x_{6} = -20.4447888830204$$
$$x_{7} = 51.8459215486945$$
$$x_{8} = -14.1723884348932$$
$$x_{9} = 20.4447888830204$$
$$x_{10} = 54.9869634999497$$
$$x_{11} = 67.5516432560125$$
$$x_{12} = -39.2826336922998$$
$$x_{13} = -42.4232846216546$$
$$x_{14} = -7.91680570747386$$
$$x_{15} = 14.1723884348932$$
$$x_{16} = 0$$
$$x_{17} = 95.8237936557983$$
$$x_{18} = 92.682377840368$$
$$x_{19} = -29.8618677162152$$
$$x_{20} = 58.1280649399539$$
$$x_{21} = 23.5831338013883$$
$$x_{22} = -64.4104114951368$$
$$x_{23} = 73.8341988749761$$
$$x_{24} = 80.1168532266283$$
$$x_{25} = -73.8341988749761$$
$$x_{26} = -67.5516432560125$$
$$x_{27} = 26.7222398348818$$
$$x_{28} = -1.8217985837127$$
$$x_{29} = -58.1280649399539$$
$$x_{30} = -17.3076165276153$$
$$x_{31} = -51.8459215486945$$
$$x_{32} = 7.91680570747386$$
$$x_{33} = -80.1168532266283$$
$$x_{34} = 1.8217985837127$$
$$x_{35} = -23.5831338013883$$
$$x_{36} = -89.5409744308928$$
$$x_{37} = 45.5640652755696$$
$$x_{38} = -36.1421462518412$$
$$x_{39} = 89.5409744308928$$
$$x_{40} = 86.3995847801759$$
$$x_{41} = 29.8618677162152$$
$$x_{42} = -86.3995847801759$$
$$x_{43} = 70.6929070794294$$
$$x_{44} = -102.10665792544$$
$$x_{45} = -45.5640652755696$$
$$x_{46} = 48.7049505853361$$
$$x_{47} = 36.1421462518412$$
Puntos máximos de la función:
$$x_{47} = -6.36114938588332$$
$$x_{47} = -87.9702777935942$$
$$x_{47} = -97.3945058407034$$
$$x_{47} = 56.5575074028724$$
$$x_{47} = -81.6875295729143$$
$$x_{47} = -59.6986350358615$$
$$x_{47} = 81.6875295729143$$
$$x_{47} = 34.5719777382463$$
$$x_{47} = -31.4318286143515$$
$$x_{47} = 22.0138459496239$$
$$x_{47} = 43.9936604673443$$
$$x_{47} = -28.2919993689317$$
$$x_{47} = 78.5461816776562$$
$$x_{47} = 15.739687460157$$
$$x_{47} = 59.6986350358615$$
$$x_{47} = -53.4164344328533$$
$$x_{47} = 28.2919993689317$$
$$x_{47} = 37.7123669872618$$
$$x_{47} = -50.275426362712$$
$$x_{47} = 9.47734088326452$$
$$x_{47} = 100.535938096812$$
$$x_{47} = -94.2530842748465$$
$$x_{47} = -43.9936604673443$$
$$x_{47} = 65.9810230816998$$
$$x_{47} = 87.9702777935942$$
$$x_{47} = 12.6059515321053$$
$$x_{47} = 94.2530842748465$$
$$x_{47} = -65.9810230816998$$
$$x_{47} = -9.47734088326452$$
$$x_{47} = -15.739687460157$$
$$x_{47} = -22.0138459496239$$
$$x_{47} = -3.28916686636117$$
$$x_{47} = 6.36114938588332$$
$$x_{47} = 50.275426362712$$
$$x_{47} = -75.4048541703099$$
$$x_{47} = -37.7123669872618$$
$$x_{47} = 72.2635497085721$$
$$x_{47} = -72.2635497085721$$
Decrece en los intervalos
$$\left[95.8237936557983, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -102.10665792544\right]$$