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$$3 x \cos{\left(3 x \right)} + \sin{\left(3 x \right)} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -14.1450206271366$$
$$x_{2} = -47.6498203678514$$
$$x_{3} = -100.008477152089$$
$$x_{4} = 23.5666593462033$$
$$x_{5} = -78.0176417347899$$
$$x_{6} = 93.7253663237826$$
$$x_{7} = 100.008477152089$$
$$x_{8} = 95.8197355146347$$
$$x_{9} = 16.2384035725192$$
$$x_{10} = -87.4422661984441$$
$$x_{11} = 49.7441173016936$$
$$x_{12} = 89.5366315785916$$
$$x_{13} = -75.9232859178705$$
$$x_{14} = 84.3007208972085$$
$$x_{15} = -25.6606697768062$$
$$x_{16} = -12.0519888065122$$
$$x_{17} = 22.5196809462695$$
$$x_{18} = -3.69517946883234$$
$$x_{19} = -84.3007208972085$$
$$x_{20} = -45.5555324591521$$
$$x_{21} = 18.3320175191655$$
$$x_{22} = 66.4987153630436$$
$$x_{23} = 3.69517946883234$$
$$x_{24} = 64.4043745938079$$
$$x_{25} = 82.2063593736386$$
$$x_{26} = 40.3198613996847$$
$$x_{27} = 92.6781821675128$$
$$x_{28} = -65.4515445438056$$
$$x_{29} = 12.0519888065122$$
$$x_{30} = -60.2157043931142$$
$$x_{31} = -53.9327340398572$$
$$x_{32} = -51.8384221669793$$
$$x_{33} = -58.1213757786594$$
$$x_{34} = 51.8384221669793$$
$$x_{35} = 60.2157043931142$$
$$x_{36} = 36.1313906251304$$
$$x_{37} = -29.8488525127497$$
$$x_{38} = 0$$
$$x_{39} = 58.1213757786594$$
$$x_{40} = 29.8488525127497$$
$$x_{41} = -9.95952883536913$$
$$x_{42} = 73.8289323297373$$
$$x_{43} = -56.0270521345864$$
$$x_{44} = -95.8197355146347$$
$$x_{45} = -91.6309983173967$$
$$x_{46} = -69.6402326441114$$
$$x_{47} = 54.9798923539233$$
$$x_{48} = -4.7358122417304$$
$$x_{49} = -27.7547382346962$$
$$x_{50} = -38.225617263561$$
$$x_{51} = -89.5366315785916$$
$$x_{52} = -34.037184713218$$
$$x_{53} = 7.8680949243268$$
$$x_{54} = 78.0176417347899$$
$$x_{55} = 0.676252612703478$$
$$x_{56} = -106.291596785411$$
$$x_{57} = 53.9327340398572$$
$$x_{58} = 62.3100374768166$$
$$x_{59} = 34.037184713218$$
$$x_{60} = -67.5458870110976$$
$$x_{61} = -93.7253663237826$$
$$x_{62} = -36.1313906251304$$
$$x_{63} = -23.5666593462033$$
$$x_{64} = 75.9232859178705$$
$$x_{65} = -97.9141058139495$$
$$x_{66} = -7.8680949243268$$
$$x_{67} = 20.4257915111899$$
$$x_{68} = 27.7547382346962$$
$$x_{69} = 42.4141204421759$$
$$x_{70} = 88.4894487126566$$
$$x_{71} = 67.5458870110976$$
$$x_{72} = -5.77879264132779$$
$$x_{73} = -80.1119996057056$$
$$x_{74} = 38.225617263561$$
$$x_{75} = -71.7345811655909$$
$$x_{76} = -73.8289323297373$$
$$x_{77} = -61.2628704049539$$
$$x_{78} = 97.9141058139495$$
$$x_{79} = 86.3950840487432$$
$$x_{80} = 31.9430036030065$$
$$x_{81} = -16.2384035725192$$
$$x_{82} = 56.0270521345864$$
$$x_{83} = 14.1450206271366$$
$$x_{84} = 9.95952883536913$$
$$x_{85} = -21.4727239072797$$
$$x_{86} = 71.7345811655909$$
$$x_{87} = 26.7076976049501$$
$$x_{88} = 80.1119996057056$$
$$x_{89} = -41.3669891991005$$
$$x_{90} = -49.7441173016936$$
$$x_{91} = 5.77879264132779$$
$$x_{92} = -31.9430036030065$$
$$x_{93} = -1.63772681314496$$
$$x_{94} = -82.2063593736386$$
$$x_{95} = -43.4612548800528$$
$$x_{96} = 44.5083922872857$$
Signos de extremos en los puntos:
(-14.145020627136628, -14.1410946924197)
(-47.64982036785143, -47.6486544974204)
(-100.00847715208945, -100.007921648254)
(23.566659346203334, 23.564302320531)
(-78.01764173478989, 78.0169296548843)
(93.7253663237826, -93.724773581063)
(100.00847715208945, -100.007921648254)
(95.81973551463474, -95.8191557274852)
(16.238403572519243, -16.234983408456)
(-87.44226619844414, -87.4416308655269)
(49.74411730169364, -49.7430005126604)
(89.53663157859164, -89.5360111065335)
(-75.92328591787046, 75.9225541956887)
(84.3007208972085, 84.3000618885604)
(-25.66066977680624, 25.6585050427546)
(-12.05198880651224, -12.0473817907474)
(22.519680946269467, -22.5172143736575)
(-3.695179468832341, -3.68023600531)
(-84.3007208972085, 84.3000618885604)
(-45.555532459152055, -45.5543129953057)
(18.332017519165465, -18.3289877498992)
(66.49871536304362, -66.4978799407601)
(3.695179468832341, -3.68023600531)
(64.40437459380786, -64.4035120058269)
(82.20635937363859, 82.2056835759154)
(40.319861399684655, 40.318483599613)
(92.6781821675128, 92.6775827274368)
(-65.45154454380558, 65.4506957559693)
(12.05198880651224, -12.0473817907474)
(-60.21570439311422, -60.2147818052389)
(-53.93273403985717, -53.9317039796355)
(-51.83842216697935, -51.8373504940684)
(-58.121375778659406, -58.1204199481347)
(51.83842216697935, -51.8373504940684)
(60.21570439311422, -60.2147818052389)
(36.131390625130436, 36.1298531252298)
(-29.848852512749733, 29.8469914576284)
(0, 0)
(58.121375778659406, -58.1204199481347)
(29.848852512749733, 29.8469914576284)
(-9.959528835369131, -9.9539553863956)
(73.82893232973727, 73.8281798509399)
(-56.027052134586405, -56.0260605764261)
(-95.81973551463474, -95.8191557274852)
(-91.63099831739673, -91.6303920268926)
(-69.64023264411136, 69.6394349069578)
(54.97989235392331, 54.9788819113479)
(-4.735812241730396, 4.72412470459143)
(-27.754738234696216, 27.7527367909844)
(-38.225617263561, 38.2241639871628)
(-89.53663157859164, -89.5360111065335)
(-34.037184713217975, 34.0355526287721)
(7.868094924326803, -7.86104354987779)
(78.01764173478989, 78.0169296548843)
(0.676252612703478, 0.606568580386551)
(-106.29159678541116, -106.291074118075)
(53.93273403985717, -53.9317039796355)
(62.31003747681657, -62.3091458971384)
(34.037184713217975, 34.0355526287721)
(-67.54588701109756, 67.5450645399848)
(-93.7253663237826, -93.724773581063)
(-36.131390625130436, 36.1298531252298)
(-23.566659346203334, 23.564302320531)
(75.92328591787046, 75.9225541956887)
(-97.91410581394948, -97.9135384281556)
(-7.868094924326803, -7.86104354987779)
(20.425791511189885, -20.4230721814922)
(27.754738234696216, 27.7527367909844)
(42.41412044217588, 42.4128106665257)
(88.4894487126566, 88.4888208980964)
(67.54588701109756, 67.5450645399848)
(-5.778792641327787, -5.76920286928617)
(-80.1119996057056, 80.111306141125)
(38.225617263561, 38.2241639871628)
(-71.73458116559091, 71.7338067182464)
(-73.82893232973727, 73.8281798509399)
(-61.262870404953894, 61.2619635861633)
(97.91410581394948, -97.9135384281556)
(86.39508404874319, 86.3944410152197)
(31.943003603006492, 31.9412645361552)
(-16.238403572519243, -16.234983408456)
(56.027052134586405, -56.0260605764261)
(14.145020627136628, -14.1410946924197)
(9.959528835369131, -9.9539553863956)
(-21.47272390727972, 21.4701371131251)
(71.73458116559091, 71.7338067182464)
(26.707697604950084, -26.7056177152197)
(80.1119996057056, 80.111306141125)
(-41.36698919910045, -41.3656462720145)
(-49.74411730169364, -49.7430005126604)
(5.778792641327787, -5.76920286928617)
(-31.943003603006492, 31.9412645361552)
(-1.6377268131449612, -1.60482329657076)
(-82.20635937363859, 82.2056835759154)
(-43.46125488005277, -43.4599766586844)
(44.50839228728569, 44.5071441357397)
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:
$$x_{1} = -14.1450206271366$$
$$x_{2} = -47.6498203678514$$
$$x_{3} = -100.008477152089$$
$$x_{4} = 93.7253663237826$$
$$x_{5} = 100.008477152089$$
$$x_{6} = 95.8197355146347$$
$$x_{7} = 16.2384035725192$$
$$x_{8} = -87.4422661984441$$
$$x_{9} = 49.7441173016936$$
$$x_{10} = 89.5366315785916$$
$$x_{11} = -12.0519888065122$$
$$x_{12} = 22.5196809462695$$
$$x_{13} = -3.69517946883234$$
$$x_{14} = -45.5555324591521$$
$$x_{15} = 18.3320175191655$$
$$x_{16} = 66.4987153630436$$
$$x_{17} = 3.69517946883234$$
$$x_{18} = 64.4043745938079$$
$$x_{19} = 12.0519888065122$$
$$x_{20} = -60.2157043931142$$
$$x_{21} = -53.9327340398572$$
$$x_{22} = -51.8384221669793$$
$$x_{23} = -58.1213757786594$$
$$x_{24} = 51.8384221669793$$
$$x_{25} = 60.2157043931142$$
$$x_{26} = 0$$
$$x_{27} = 58.1213757786594$$
$$x_{28} = -9.95952883536913$$
$$x_{29} = -56.0270521345864$$
$$x_{30} = -95.8197355146347$$
$$x_{31} = -91.6309983173967$$
$$x_{32} = -89.5366315785916$$
$$x_{33} = 7.8680949243268$$
$$x_{34} = -106.291596785411$$
$$x_{35} = 53.9327340398572$$
$$x_{36} = 62.3100374768166$$
$$x_{37} = -93.7253663237826$$
$$x_{38} = -97.9141058139495$$
$$x_{39} = -7.8680949243268$$
$$x_{40} = 20.4257915111899$$
$$x_{41} = -5.77879264132779$$
$$x_{42} = 97.9141058139495$$
$$x_{43} = -16.2384035725192$$
$$x_{44} = 56.0270521345864$$
$$x_{45} = 14.1450206271366$$
$$x_{46} = 9.95952883536913$$
$$x_{47} = 26.7076976049501$$
$$x_{48} = -41.3669891991005$$
$$x_{49} = -49.7441173016936$$
$$x_{50} = 5.77879264132779$$
$$x_{51} = -1.63772681314496$$
$$x_{52} = -43.4612548800528$$
Puntos máximos de la función:
$$x_{52} = 23.5666593462033$$
$$x_{52} = -78.0176417347899$$
$$x_{52} = -75.9232859178705$$
$$x_{52} = 84.3007208972085$$
$$x_{52} = -25.6606697768062$$
$$x_{52} = -84.3007208972085$$
$$x_{52} = 82.2063593736386$$
$$x_{52} = 40.3198613996847$$
$$x_{52} = 92.6781821675128$$
$$x_{52} = -65.4515445438056$$
$$x_{52} = 36.1313906251304$$
$$x_{52} = -29.8488525127497$$
$$x_{52} = 29.8488525127497$$
$$x_{52} = 73.8289323297373$$
$$x_{52} = -69.6402326441114$$
$$x_{52} = 54.9798923539233$$
$$x_{52} = -4.7358122417304$$
$$x_{52} = -27.7547382346962$$
$$x_{52} = -38.225617263561$$
$$x_{52} = -34.037184713218$$
$$x_{52} = 78.0176417347899$$
$$x_{52} = 0.676252612703478$$
$$x_{52} = 34.037184713218$$
$$x_{52} = -67.5458870110976$$
$$x_{52} = -36.1313906251304$$
$$x_{52} = -23.5666593462033$$
$$x_{52} = 75.9232859178705$$
$$x_{52} = 27.7547382346962$$
$$x_{52} = 42.4141204421759$$
$$x_{52} = 88.4894487126566$$
$$x_{52} = 67.5458870110976$$
$$x_{52} = -80.1119996057056$$
$$x_{52} = 38.225617263561$$
$$x_{52} = -71.7345811655909$$
$$x_{52} = -73.8289323297373$$
$$x_{52} = -61.2628704049539$$
$$x_{52} = 86.3950840487432$$
$$x_{52} = 31.9430036030065$$
$$x_{52} = -21.4727239072797$$
$$x_{52} = 71.7345811655909$$
$$x_{52} = 80.1119996057056$$
$$x_{52} = -31.9430036030065$$
$$x_{52} = -82.2063593736386$$
$$x_{52} = 44.5083922872857$$
Decrece en los intervalos
$$\left[100.008477152089, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -106.291596785411\right]$$