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$$\frac{3 x \cos{\left(3 x \right)}}{5} + \frac{\sin{\left(3 x \right)}}{5} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -82.2063593736386$$
$$x_{2} = 16.2384035725192$$
$$x_{3} = -4.7358122417304$$
$$x_{4} = -51.8384221669793$$
$$x_{5} = 56.0270521345864$$
$$x_{6} = 84.3007208972085$$
$$x_{7} = -89.5366315785916$$
$$x_{8} = 67.5458870110976$$
$$x_{9} = 49.7441173016936$$
$$x_{10} = 26.7076976049501$$
$$x_{11} = -80.1119996057056$$
$$x_{12} = 80.1119996057056$$
$$x_{13} = 31.9430036030065$$
$$x_{14} = 73.8289323297373$$
$$x_{15} = 66.4987153630436$$
$$x_{16} = 22.5196809462695$$
$$x_{17} = -87.4422661984441$$
$$x_{18} = -14.1450206271366$$
$$x_{19} = 0.676252612703478$$
$$x_{20} = -23.5666593462033$$
$$x_{21} = -75.9232859178705$$
$$x_{22} = 89.5366315785916$$
$$x_{23} = 0$$
$$x_{24} = -58.1213757786594$$
$$x_{25} = 27.7547382346962$$
$$x_{26} = -36.1313906251304$$
$$x_{27} = 58.1213757786594$$
$$x_{28} = -5.77879264132779$$
$$x_{29} = 62.3100374768166$$
$$x_{30} = -43.4612548800528$$
$$x_{31} = 88.4894487126566$$
$$x_{32} = -1.63772681314496$$
$$x_{33} = 92.6781821675128$$
$$x_{34} = 9.95952883536913$$
$$x_{35} = -49.7441173016936$$
$$x_{36} = -29.8488525127497$$
$$x_{37} = -38.225617263561$$
$$x_{38} = 12.0519888065122$$
$$x_{39} = 78.0176417347899$$
$$x_{40} = 60.2157043931142$$
$$x_{41} = 18.3320175191655$$
$$x_{42} = 3.69517946883234$$
$$x_{43} = 100.008477152089$$
$$x_{44} = -69.6402326441114$$
$$x_{45} = -3.69517946883234$$
$$x_{46} = -45.5555324591521$$
$$x_{47} = -9.95952883536913$$
$$x_{48} = 86.3950840487432$$
$$x_{49} = 53.9327340398572$$
$$x_{50} = -73.8289323297373$$
$$x_{51} = -60.2157043931142$$
$$x_{52} = 14.1450206271366$$
$$x_{53} = 75.9232859178705$$
$$x_{54} = -41.3669891991005$$
$$x_{55} = -16.2384035725192$$
$$x_{56} = 7.8680949243268$$
$$x_{57} = 29.8488525127497$$
$$x_{58} = 64.4043745938079$$
$$x_{59} = -97.9141058139495$$
$$x_{60} = 97.9141058139495$$
$$x_{61} = 23.5666593462033$$
$$x_{62} = -53.9327340398572$$
$$x_{63} = -7.8680949243268$$
$$x_{64} = -25.6606697768062$$
$$x_{65} = -61.2628704049539$$
$$x_{66} = 34.037184713218$$
$$x_{67} = 5.77879264132779$$
$$x_{68} = -31.9430036030065$$
$$x_{69} = -67.5458870110976$$
$$x_{70} = -12.0519888065122$$
$$x_{71} = -95.8197355146347$$
$$x_{72} = -100.008477152089$$
$$x_{73} = 42.4141204421759$$
$$x_{74} = -34.037184713218$$
$$x_{75} = 36.1313906251304$$
$$x_{76} = -84.3007208972085$$
$$x_{77} = 51.8384221669793$$
$$x_{78} = -47.6498203678514$$
$$x_{79} = -27.7547382346962$$
$$x_{80} = 38.225617263561$$
$$x_{81} = -91.6309983173967$$
$$x_{82} = 54.9798923539233$$
$$x_{83} = -21.4727239072797$$
$$x_{84} = -65.4515445438056$$
$$x_{85} = -93.7253663237826$$
$$x_{86} = 40.3198613996847$$
$$x_{87} = -71.7345811655909$$
$$x_{88} = -106.291596785411$$
$$x_{89} = 95.8197355146347$$
$$x_{90} = 44.5083922872857$$
$$x_{91} = -56.0270521345864$$
$$x_{92} = 82.2063593736386$$
$$x_{93} = 93.7253663237826$$
$$x_{94} = 71.7345811655909$$
$$x_{95} = -78.0176417347899$$
$$x_{96} = 20.4257915111899$$
Signos de extremos en los puntos:
(-82.20635937363859, 16.4411367151831)
(16.238403572519243, -3.2469966816912)
(-4.735812241730396, 0.944824940918285)
(-51.83842216697935, -10.3674700988137)
(56.027052134586405, -11.2052121152852)
(84.3007208972085, 16.8600123777121)
(-89.53663157859164, -17.9072022213067)
(67.54588701109756, 13.509012907997)
(49.74411730169364, -9.94860010253207)
(26.707697604950084, -5.34112354304395)
(-80.1119996057056, 16.022261228225)
(80.1119996057056, 16.022261228225)
(31.943003603006492, 6.38825290723105)
(73.82893232973727, 14.765635970188)
(66.49871536304362, -13.299575988152)
(22.519680946269467, -4.5034428747315)
(-87.44226619844414, -17.4883261731054)
(-14.145020627136628, -2.82821893848394)
(0.676252612703478, 0.12131371607731)
(-23.566659346203334, 4.71286046410621)
(-75.92328591787046, 15.1845108391377)
(89.53663157859164, -17.9072022213067)
(0, 0)
(-58.121375778659406, -11.6240839896269)
(27.754738234696216, 5.55054735819688)
(-36.131390625130436, 7.22597062504596)
(58.121375778659406, -11.6240839896269)
(-5.778792641327787, -1.15384057385723)
(62.31003747681657, -12.4618291794277)
(-43.46125488005277, -8.69199533173688)
(88.4894487126566, 17.6977641796193)
(-1.6377268131449612, -0.320964659314151)
(92.6781821675128, 18.5355165454874)
(9.959528835369131, -1.99079107727912)
(-49.74411730169364, -9.94860010253207)
(-29.848852512749733, 5.96939829152568)
(-38.225617263561, 7.64483279743256)
(12.05198880651224, -2.40947635814947)
(78.01764173478989, 15.6033859309769)
(60.21570439311422, -12.0429563610478)
(18.332017519165465, -3.66579754997984)
(3.695179468832341, -0.736047201062)
(100.00847715208945, -20.0015843296507)
(-69.64023264411136, 13.9278869813916)
(-3.695179468832341, -0.736047201062)
(-45.555532459152055, -9.11086259906113)
(-9.959528835369131, -1.99079107727912)
(86.39508404874319, 17.2788882030439)
(53.93273403985717, -10.7863407959271)
(-73.82893232973727, 14.765635970188)
(-60.21570439311422, -12.0429563610478)
(14.145020627136628, -2.82821893848394)
(75.92328591787046, 15.1845108391377)
(-41.36698919910045, -8.2731292544029)
(-16.238403572519243, -3.2469966816912)
(7.868094924326803, -1.57220870997556)
(29.848852512749733, 5.96939829152568)
(64.40437459380786, -12.8807024011654)
(-97.91410581394948, -19.5827076856311)
(97.91410581394948, -19.5827076856311)
(23.566659346203334, 4.71286046410621)
(-53.93273403985717, -10.7863407959271)
(-7.868094924326803, -1.57220870997556)
(-25.66066977680624, 5.13170100855091)
(-61.262870404953894, 12.2523927172327)
(34.037184713217975, 6.80711052575443)
(5.778792641327787, -1.15384057385723)
(-31.943003603006492, 6.38825290723105)
(-67.54588701109756, 13.509012907997)
(-12.05198880651224, -2.40947635814947)
(-95.81973551463474, -19.163831145497)
(-100.00847715208945, -20.0015843296507)
(42.41412044217588, 8.48256213330513)
(-34.037184713217975, 6.80711052575443)
(36.131390625130436, 7.22597062504596)
(-84.3007208972085, 16.8600123777121)
(51.83842216697935, -10.3674700988137)
(-47.64982036785143, -9.52973089948409)
(-27.754738234696216, 5.55054735819688)
(38.225617263561, 7.64483279743256)
(-91.63099831739673, -18.3260784053785)
(54.97989235392331, 10.9957763822696)
(-21.47272390727972, 4.29402742262502)
(-65.45154454380558, 13.0901391511939)
(-93.7253663237826, -18.7449547162126)
(40.319861399684655, 8.0636967199226)
(-71.73458116559091, 14.3467613436493)
(-106.29159678541116, -21.2582148236149)
(95.81973551463474, -19.163831145497)
(44.50839228728569, 8.90142882714793)
(-56.027052134586405, -11.2052121152852)
(82.20635937363859, 16.4411367151831)
(93.7253663237826, -18.7449547162126)
(71.73458116559091, 14.3467613436493)
(-78.01764173478989, 15.6033859309769)
(20.425791511189885, -4.08461443629844)
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:
$$x_{1} = 16.2384035725192$$
$$x_{2} = -51.8384221669793$$
$$x_{3} = 56.0270521345864$$
$$x_{4} = -89.5366315785916$$
$$x_{5} = 49.7441173016936$$
$$x_{6} = 26.7076976049501$$
$$x_{7} = 66.4987153630436$$
$$x_{8} = 22.5196809462695$$
$$x_{9} = -87.4422661984441$$
$$x_{10} = -14.1450206271366$$
$$x_{11} = 89.5366315785916$$
$$x_{12} = 0$$
$$x_{13} = -58.1213757786594$$
$$x_{14} = 58.1213757786594$$
$$x_{15} = -5.77879264132779$$
$$x_{16} = 62.3100374768166$$
$$x_{17} = -43.4612548800528$$
$$x_{18} = -1.63772681314496$$
$$x_{19} = 9.95952883536913$$
$$x_{20} = -49.7441173016936$$
$$x_{21} = 12.0519888065122$$
$$x_{22} = 60.2157043931142$$
$$x_{23} = 18.3320175191655$$
$$x_{24} = 3.69517946883234$$
$$x_{25} = 100.008477152089$$
$$x_{26} = -3.69517946883234$$
$$x_{27} = -45.5555324591521$$
$$x_{28} = -9.95952883536913$$
$$x_{29} = 53.9327340398572$$
$$x_{30} = -60.2157043931142$$
$$x_{31} = 14.1450206271366$$
$$x_{32} = -41.3669891991005$$
$$x_{33} = -16.2384035725192$$
$$x_{34} = 7.8680949243268$$
$$x_{35} = 64.4043745938079$$
$$x_{36} = -97.9141058139495$$
$$x_{37} = 97.9141058139495$$
$$x_{38} = -53.9327340398572$$
$$x_{39} = -7.8680949243268$$
$$x_{40} = 5.77879264132779$$
$$x_{41} = -12.0519888065122$$
$$x_{42} = -95.8197355146347$$
$$x_{43} = -100.008477152089$$
$$x_{44} = 51.8384221669793$$
$$x_{45} = -47.6498203678514$$
$$x_{46} = -91.6309983173967$$
$$x_{47} = -93.7253663237826$$
$$x_{48} = -106.291596785411$$
$$x_{49} = 95.8197355146347$$
$$x_{50} = -56.0270521345864$$
$$x_{51} = 93.7253663237826$$
$$x_{52} = 20.4257915111899$$
Puntos máximos de la función:
$$x_{52} = -82.2063593736386$$
$$x_{52} = -4.7358122417304$$
$$x_{52} = 84.3007208972085$$
$$x_{52} = 67.5458870110976$$
$$x_{52} = -80.1119996057056$$
$$x_{52} = 80.1119996057056$$
$$x_{52} = 31.9430036030065$$
$$x_{52} = 73.8289323297373$$
$$x_{52} = 0.676252612703478$$
$$x_{52} = -23.5666593462033$$
$$x_{52} = -75.9232859178705$$
$$x_{52} = 27.7547382346962$$
$$x_{52} = -36.1313906251304$$
$$x_{52} = 88.4894487126566$$
$$x_{52} = 92.6781821675128$$
$$x_{52} = -29.8488525127497$$
$$x_{52} = -38.225617263561$$
$$x_{52} = 78.0176417347899$$
$$x_{52} = -69.6402326441114$$
$$x_{52} = 86.3950840487432$$
$$x_{52} = -73.8289323297373$$
$$x_{52} = 75.9232859178705$$
$$x_{52} = 29.8488525127497$$
$$x_{52} = 23.5666593462033$$
$$x_{52} = -25.6606697768062$$
$$x_{52} = -61.2628704049539$$
$$x_{52} = 34.037184713218$$
$$x_{52} = -31.9430036030065$$
$$x_{52} = -67.5458870110976$$
$$x_{52} = 42.4141204421759$$
$$x_{52} = -34.037184713218$$
$$x_{52} = 36.1313906251304$$
$$x_{52} = -84.3007208972085$$
$$x_{52} = -27.7547382346962$$
$$x_{52} = 38.225617263561$$
$$x_{52} = 54.9798923539233$$
$$x_{52} = -21.4727239072797$$
$$x_{52} = -65.4515445438056$$
$$x_{52} = 40.3198613996847$$
$$x_{52} = -71.7345811655909$$
$$x_{52} = 44.5083922872857$$
$$x_{52} = 82.2063593736386$$
$$x_{52} = 71.7345811655909$$
$$x_{52} = -78.0176417347899$$
Decrece en los intervalos
$$\left[100.008477152089, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -106.291596785411\right]$$