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$$- \frac{3 x \sin^{2}{\left(\frac{3 x}{5} \right)} \sin{\left(\frac{3 x^{2}}{10} \right)}}{5} + \frac{6 \sin{\left(\frac{3 x}{5} \right)} \cos{\left(\frac{3 x}{5} \right)} \cos{\left(\frac{3 x^{2}}{10} \right)}}{5} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 12.1229824381761$$
$$x_{2} = -65.6843933727047$$
$$x_{3} = 3.13113402113334$$
$$x_{4} = 36.7819344329021$$
$$x_{5} = -31.7237228244603$$
$$x_{6} = 60.1068937789405$$
$$x_{7} = 88.8543310730566$$
$$x_{8} = 52.2615470317133$$
$$x_{9} = 94.4598843953214$$
$$x_{10} = -89.3310053485053$$
$$x_{11} = -73.5135729831908$$
$$x_{12} = -15.707963267949$$
$$x_{13} = -11.6944767794746$$
$$x_{14} = -83.7448097110512$$
$$x_{15} = -91.7576303504263$$
$$x_{16} = -19.936259585824$$
$$x_{17} = 95.9422194402264$$
$$x_{18} = 14.09408526094$$
$$x_{19} = -96.4320105798712$$
$$x_{20} = 37.879473611331$$
$$x_{21} = 99.4837673636768$$
$$x_{22} = 48.0007642143196$$
$$x_{23} = -33.6306745660586$$
$$x_{24} = 50.2364958899188$$
$$x_{25} = -21.721908390206$$
$$x_{26} = -80.6419446072301$$
$$x_{27} = -30.0065529310323$$
$$x_{28} = -10.471975511966$$
$$x_{29} = 99.7436693920312$$
$$x_{30} = 4.33188285755461$$
$$x_{31} = -55.8621401192102$$
$$x_{32} = -52.5880166938635$$
$$x_{33} = -37.7414741229502$$
$$x_{34} = 44.2524858552252$$
$$x_{35} = -68.0708694375468$$
$$x_{36} = -85.3116773421505$$
$$x_{37} = -5.82391963347914$$
$$x_{38} = -7.92441056952944$$
$$x_{39} = 31.4159265358979$$
$$x_{40} = 94.2477796076938$$
$$x_{41} = -50.2364958899188$$
$$x_{42} = -26.0420466134315$$
$$x_{43} = 38.1541974640602$$
$$x_{44} = 73.8657984508439$$
$$x_{45} = -35.7389993261695$$
$$x_{46} = -63.0067797559502$$
$$x_{47} = 78.4595441521704$$
$$x_{48} = 82.248610897273$$
$$x_{49} = 23.9975905109106$$
$$x_{50} = 1.57411458733581$$
$$x_{51} = 5.82391963347914$$
$$x_{52} = -77.9997678736386$$
$$x_{53} = -57.8052881194235$$
$$x_{54} = 68.0154824215815$$
$$x_{55} = 31.7237228244603$$
$$x_{56} = 58.2511405363585$$
$$x_{57} = 62.2442013680375$$
$$x_{58} = -13.7223199085531$$
$$x_{59} = 69.6318519740652$$
$$x_{60} = -73.0756715190628$$
$$x_{61} = -53.7622175617027$$
$$x_{62} = -94.0098795829772$$
$$x_{63} = 72.9339457850776$$
$$x_{64} = 80.2515741614971$$
$$x_{65} = 76.5101444891375$$
$$x_{66} = 89.0078563237483$$
$$x_{67} = -89.2149356986415$$
$$x_{68} = 17.4331276401965$$
$$x_{69} = -63.7440034171542$$
$$x_{70} = -41.8835996793582$$
$$x_{71} = 22.1924510958835$$
$$x_{72} = 16.2184676662057$$
$$x_{73} = -26.1799387799149$$
$$x_{74} = 54.2465002870835$$
$$x_{75} = -47.3498033640974$$
$$x_{76} = -39.6328034914763$$
$$x_{77} = -4.33188285755461$$
$$x_{78} = 7.92441056952944$$
$$x_{79} = -97.9401776591651$$
$$x_{80} = 20.1924350450536$$
$$x_{81} = 83.8942472369898$$
$$x_{82} = 86.1055874271444$$
$$x_{83} = 0$$
$$x_{84} = 45.7630668857082$$
$$x_{85} = 41.9735858539592$$
$$x_{86} = 10.1128795090719$$
$$x_{87} = -47.8919861327274$$
$$x_{88} = -59.7576352717305$$
$$x_{89} = 66.0023260880075$$
$$x_{90} = 20.943951023932$$
$$x_{91} = 34.2466972080798$$
$$x_{92} = 56.2354443005911$$
$$x_{93} = -69.9318160427244$$
$$x_{94} = -99.6400212424982$$
$$x_{95} = -81.9298215839724$$
$$x_{96} = -75.7538875442276$$
$$x_{97} = 26.186626750821$$
$$x_{98} = -27.8402787235296$$
$$x_{99} = 62.8609426250491$$
$$x_{100} = -1.57411458733581$$
Signos de extremos en los puntos:
(12.122982438176072, 0.495439634053406)
(-65.68439337270475, 0.780316943676428)
(3.1311340211333363, -1.08999126604949)
(36.78193443290206, -0.204985961287315)
(-31.7237228244603, -0.168050506243539)
(60.10689377894048, -1.19588439917299)
(88.85433107305663, -0.191341641142858)
(52.26154703171333, -0.202917876124195)
(94.45988439532135, -0.18410751714817)
(-89.3310053485053, -0.164002502563617)
(-73.5135729831908, -0.184598138754976)
(-15.707963267948966, -0.2)
(-11.694476779474574, -0.640337701401968)
(-83.7448097110512, -0.199787532971672)
(-91.75763035042625, 0.794126207264612)
(-19.936259585823986, 0.119776909853067)
(95.94221944022644, -0.923047352632901)
(14.094085260939979, -0.875664717267834)
(-96.43201057987125, 0.733767223026068)
(37.879473611331, -0.650452170951313)
(99.48376736367679, -0.2)
(48.00076421431957, 0.0515440249608699)
(-33.630674566058595, 0.742493286590499)
(50.236495889918785, -1.11441671326918)
(-21.72190839020604, -0.399209306910576)
(-80.64194460723007, -1.10718977219525)
(-30.006552931032346, 0.35910584967736)
(-10.471975511965978, -0.2)
(99.74366939203122, -0.176072633940323)
(4.3318828575546116, 0.0115793187313457)
(-55.86214011921016, 0.543782261197991)
(-52.58801669386346, -0.182051216332967)
(-37.741474122950194, 0.168972427432094)
(44.25248585522518, -1.17703617181545)
(-68.07086943754685, -0.199999796161617)
(-85.31167734215052, -0.834349949338148)
(-5.823919633479142, -0.287284389954009)
(-7.9244105695294405, 0.798158544445862)
(31.41592653589793, -0.2)
(94.2477796076938, -0.2)
(-50.236495889918785, -1.11441671326918)
(-26.04204661343155, -0.205010729742474)
(38.15419746406023, -0.814406348788211)
(73.86579845084388, -0.309122850092553)
(-35.73899932616946, 0.0700640897824696)
(-63.00677975595021, -0.210508659248956)
(78.4595441521704, -0.1979509813381)
(82.24861089727298, 0.429317438751723)
(23.997590510910637, -1.1329867259313)
(1.5741145873358113, 0.283245446606709)
(5.823919633479142, -0.287284389954009)
(-77.99976787363863, -0.301077139843918)
(-57.8052881194235, -0.215147988824541)
(68.01548242158147, -0.199279610133012)
(31.7237228244603, -0.168050506243539)
(58.251140536358484, -0.0537240222852314)
(62.24420136803749, -0.0811988567497575)
(-13.722319908553107, 0.661370704411558)
(69.6318519740652, -0.850487500941559)
(-73.0756715190628, -0.181733756148313)
(-53.76221756170269, 0.355581748402606)
(-94.00987958297723, -0.179981430174821)
(72.93394578507758, -0.151904392214644)
(80.25157416149706, -0.93227455078432)
(76.51014448913746, -1.08044513961129)
(89.00785632374833, -0.200000582741816)
(-89.21493569864154, -0.185458665369386)
(17.4331276401965, -0.937741164942956)
(-63.74400341715418, 0.0704320815719325)
(-41.883599679358234, -0.199999640286369)
(22.192451095883523, -0.661571265986302)
(16.218467666205665, -0.284711532019328)
(-26.179938779914945, -0.2)
(54.24650028708346, -1.01935942458116)
(-47.34980336409741, -0.18255636863491)
(-39.63280349147627, 0.753275602992737)
(-4.3318828575546116, 0.0115793187313457)
(7.9244105695294405, 0.798158544445862)
(-97.94017765916512, 0.438828621083014)
(20.19243504505362, -0.386054928630667)
(83.8942472369898, -0.195219108292072)
(86.10558742714439, 0.770385386183498)
(0, -1/5)
(45.7630668857082, 0.330628292915112)
(41.97358585395921, -0.198062458158328)
(10.112879509071856, -0.166087039538411)
(-47.89198613272742, -0.397076999169344)
(-59.757635271730514, -1.12688150616752)
(66.00232608800746, 0.694033745010953)
(20.943951023931955, -0.2)
(34.24669720807977, 0.783762087428377)
(56.23544430059111, 0.330538403541457)
(-69.93181604272439, -1.00883448566664)
(-99.64002124249825, -0.191429329624297)
(-81.92982158397238, -1.00029303609286)
(-75.75388754422764, 0.789878017542022)
(26.18662675082099, -0.200000844865974)
(-27.840278723529604, 0.50385476335627)
(62.86094262504909, -0.200146513330916)
(-1.5741145873358113, 0.283245446606709)
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:
$$x_{1} = 3.13113402113334$$
$$x_{2} = 36.7819344329021$$
$$x_{3} = 60.1068937789405$$
$$x_{4} = 52.2615470317133$$
$$x_{5} = -15.707963267949$$
$$x_{6} = -11.6944767794746$$
$$x_{7} = 95.9422194402264$$
$$x_{8} = 14.09408526094$$
$$x_{9} = 37.879473611331$$
$$x_{10} = 50.2364958899188$$
$$x_{11} = -21.721908390206$$
$$x_{12} = -80.6419446072301$$
$$x_{13} = -10.471975511966$$
$$x_{14} = 44.2524858552252$$
$$x_{15} = -85.3116773421505$$
$$x_{16} = -5.82391963347914$$
$$x_{17} = 31.4159265358979$$
$$x_{18} = 94.2477796076938$$
$$x_{19} = -50.2364958899188$$
$$x_{20} = -26.0420466134315$$
$$x_{21} = 38.1541974640602$$
$$x_{22} = 73.8657984508439$$
$$x_{23} = -63.0067797559502$$
$$x_{24} = 23.9975905109106$$
$$x_{25} = 5.82391963347914$$
$$x_{26} = -77.9997678736386$$
$$x_{27} = -57.8052881194235$$
$$x_{28} = 69.6318519740652$$
$$x_{29} = 80.2515741614971$$
$$x_{30} = 76.5101444891375$$
$$x_{31} = 89.0078563237483$$
$$x_{32} = 17.4331276401965$$
$$x_{33} = 22.1924510958835$$
$$x_{34} = 16.2184676662057$$
$$x_{35} = 54.2465002870835$$
$$x_{36} = 20.1924350450536$$
$$x_{37} = 0$$
$$x_{38} = -47.8919861327274$$
$$x_{39} = -59.7576352717305$$
$$x_{40} = 20.943951023932$$
$$x_{41} = -69.9318160427244$$
$$x_{42} = -81.9298215839724$$
$$x_{43} = 26.186626750821$$
$$x_{44} = 62.8609426250491$$
Puntos máximos de la función:
$$x_{44} = 12.1229824381761$$
$$x_{44} = -65.6843933727047$$
$$x_{44} = -31.7237228244603$$
$$x_{44} = 88.8543310730566$$
$$x_{44} = 94.4598843953214$$
$$x_{44} = -89.3310053485053$$
$$x_{44} = -73.5135729831908$$
$$x_{44} = -83.7448097110512$$
$$x_{44} = -91.7576303504263$$
$$x_{44} = -19.936259585824$$
$$x_{44} = -96.4320105798712$$
$$x_{44} = 99.4837673636768$$
$$x_{44} = 48.0007642143196$$
$$x_{44} = -33.6306745660586$$
$$x_{44} = -30.0065529310323$$
$$x_{44} = 99.7436693920312$$
$$x_{44} = 4.33188285755461$$
$$x_{44} = -55.8621401192102$$
$$x_{44} = -52.5880166938635$$
$$x_{44} = -37.7414741229502$$
$$x_{44} = -68.0708694375468$$
$$x_{44} = -7.92441056952944$$
$$x_{44} = -35.7389993261695$$
$$x_{44} = 78.4595441521704$$
$$x_{44} = 82.248610897273$$
$$x_{44} = 1.57411458733581$$
$$x_{44} = 68.0154824215815$$
$$x_{44} = 31.7237228244603$$
$$x_{44} = 58.2511405363585$$
$$x_{44} = 62.2442013680375$$
$$x_{44} = -13.7223199085531$$
$$x_{44} = -73.0756715190628$$
$$x_{44} = -53.7622175617027$$
$$x_{44} = -94.0098795829772$$
$$x_{44} = 72.9339457850776$$
$$x_{44} = -89.2149356986415$$
$$x_{44} = -63.7440034171542$$
$$x_{44} = -41.8835996793582$$
$$x_{44} = -26.1799387799149$$
$$x_{44} = -47.3498033640974$$
$$x_{44} = -39.6328034914763$$
$$x_{44} = -4.33188285755461$$
$$x_{44} = 7.92441056952944$$
$$x_{44} = -97.9401776591651$$
$$x_{44} = 83.8942472369898$$
$$x_{44} = 86.1055874271444$$
$$x_{44} = 45.7630668857082$$
$$x_{44} = 41.9735858539592$$
$$x_{44} = 10.1128795090719$$
$$x_{44} = 66.0023260880075$$
$$x_{44} = 34.2466972080798$$
$$x_{44} = 56.2354443005911$$
$$x_{44} = -99.6400212424982$$
$$x_{44} = -75.7538875442276$$
$$x_{44} = -27.8402787235296$$
$$x_{44} = -1.57411458733581$$
Decrece en los intervalos
$$\left[95.9422194402264, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -85.3116773421505\right]$$