Para hallar los extremos hay que resolver la ecuación
$$\frac{d}{d t} f{\left(t \right)} = 0$$
(la derivada es igual a cero),
y las raíces de esta ecuación serán los extremos de esta función:
$$\frac{d}{d t} f{\left(t \right)} = $$
primera derivada$$- \frac{4 \left(- \sin{\left(\frac{8 t}{5} \right)} - \cos{\left(\frac{8 t}{5} \right)}\right) e^{\frac{\left(-1\right) 4 t}{5}}}{5} + \left(\frac{8 \sin{\left(\frac{8 t}{5} \right)}}{5} - \frac{8 \cos{\left(\frac{8 t}{5} \right)}}{5}\right) e^{\frac{\left(-1\right) 4 t}{5}} + 160 \sin{\left(2 t \right)} - 40 \cos{\left(2 t \right)} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$t_{1} = 22.1136379067686$$
$$t_{2} = 31.5384158674614$$
$$t_{3} = 29.9676195406663$$
$$t_{4} = 50.3879717890001$$
$$t_{5} = 72.3791203641287$$
$$t_{6} = 100.653454246437$$
$$t_{7} = 45.6755828086154$$
$$t_{8} = 77.0915093445134$$
$$t_{9} = 14.2596562316776$$
$$t_{10} = 64.5251387301542$$
$$t_{11} = 67.666731383744$$
$$t_{12} = 37.821601174641$$
$$t_{13} = -33.1783278478226$$
$$t_{14} = 231.029549370413$$
$$t_{15} = 36.2508048478461$$
$$t_{16} = 56.6711570961797$$
$$t_{17} = -25.3243462519939$$
$$t_{18} = -7.63561646197875$$
$$t_{19} = 97.511861592847$$
$$t_{20} = 95.9410652660521$$
$$t_{21} = 94.3702689392572$$
$$t_{22} = -39.0688140733743$$
$$t_{23} = 9.54726476204874$$
$$t_{24} = -29.2513370331717$$
$$t_{25} = 59.8127497497695$$
$$t_{26} = -23.3608507566309$$
$$t_{27} = -13.5440223795782$$
$$t_{28} = 34.6800085210512$$
$$t_{29} = 88.0870836320776$$
$$t_{30} = 86.5162873052827$$
$$t_{31} = -19.4338528652826$$
$$t_{32} = -11.5836856349292$$
$$t_{33} = 6.4056966162943$$
$$t_{34} = 80.2331019981032$$
$$t_{35} = 28.3968232138706$$
$$t_{36} = 58.2419534229746$$
$$t_{37} = -31.2148324394912$$
$$t_{38} = -9.62753408038416$$
$$t_{39} = 253.020697945542$$
$$t_{40} = 42.5339901550256$$
$$t_{41} = -27.2878416357148$$
$$t_{42} = 1.6946360179382$$
$$t_{43} = -5.01188415768002$$
$$t_{44} = 0.123351471449465$$
$$t_{45} = -1.45978595831549$$
$$t_{46} = 73.9499166909236$$
$$t_{47} = 51.958768115795$$
$$t_{48} = 89.6578799588725$$
$$t_{49} = 20.5428415804029$$
$$t_{50} = 53.5295644425899$$
$$t_{51} = 78.6623056713083$$
$$t_{52} = -35.1418232563624$$
$$t_{53} = 66.0959350569491$$
$$t_{54} = -37.1053186648767$$
$$t_{55} = -15.5068952914144$$
$$t_{56} = 75.5207130177185$$
$$t_{57} = 23.6844342334812$$
$$t_{58} = 15.8304526025542$$
$$t_{59} = 81.8038983248981$$
$$t_{60} = 7.97646933662247$$
$$t_{61} = -17.4703441920742$$
$$t_{62} = 44.1047864818205$$
$$t_{63} = 12.6888596750542$$
$$t_{64} = -21.3973541839018$$
$$t_{65} = 55.1003607693848$$
Signos de extremos en los puntos:
(22.113637906768624, -82.4621124830361)
(31.538415867461374, -82.4621125123662)
(29.967619540666323, 82.462112512408)
(50.387971789000126, -82.4621125123532)
(72.37912036412868, -82.4621125123532)
(100.65345424643681, -82.4621125123532)
(45.67558280861543, 82.4621125123532)
(77.09150934451337, 82.4621125123532)
(14.25965623167759, 82.462128211435)
(64.5251387301542, 82.4621125123532)
(67.666731383744, 82.4621125123532)
(37.82160117464095, -82.4621125123531)
(-33.17832784782255, 425982495967.921)
(231.02954937041324, 82.4621125123532)
(36.250804847846055, 82.4621125123529)
(56.67115709617971, -82.4621125123532)
(-25.32434625199387, 795497849.085983)
(-7.63561646197875, -495.470592521725)
(97.51186159284703, -82.4621125123532)
(95.94106526605212, 82.4621125123532)
(94.37026893925723, -82.4621125123532)
(-39.06881407337434, -47419425119204.6)
(9.547264762048739, -82.4618768751647)
(-29.25133703317167, 18408372808.1336)
(59.8127497497695, -82.4621125123532)
(-23.36085075663088, -165367688.280377)
(-13.54402237957821, 64244.8026639157)
(34.680008521051164, -82.4621125123529)
(88.08708363207764, -82.4621125123532)
(86.51628730528275, 82.4621125123532)
(-19.433852865282553, -7146202.19545918)
(-11.583685634929193, -13332.4991441387)
(6.405696616294296, -82.4537058648811)
(80.23310199810317, 82.4621125123532)
(28.396823213870626, -82.4621125125044)
(58.24195342297461, 82.4621125123532)
(-31.21483243949115, -88553060862.2272)
(-9.627534080384159, 2707.99611206471)
(253.0206979455418, 82.4621125123532)
(42.53399015502564, 82.4621125123532)
(-27.28784163571483, -3826724717.67707)
(1.694636017938203, 82.5885965797596)
(-5.011884157680023, 118.222373155984)
(0.1233514714494654, -83.5280907318408)
(-1.4597859583154935, 86.9861261826466)
(73.94991669092357, 82.4621125123532)
(51.95876811579502, 82.4621125123532)
(89.65787995887254, 82.4621125123532)
(20.542841580402918, 82.4621124313744)
(53.529564442589916, -82.4621125123532)
(78.66230567130826, -82.4621125123532)
(-35.14182325636243, -2049179161232.81)
(66.09593505694909, -82.4621125123532)
(-37.10531866487666, 9857530004545.41)
(-15.50689529141443, -308896.285160714)
(75.52071301771846, -82.4621125123532)
(23.684434233481202, 82.4621125054119)
(15.830452602554237, -82.4621162293517)
(81.80389832489806, -82.4621125123532)
(7.976469336622474, 82.4601220911188)
(-17.470344192074243, 1485613.52149387)
(44.10478648182054, -82.4621125123532)
(12.688859675054172, -82.4621558758268)
(-21.397354183901783, 34376533.4513548)
(55.100360769384814, 82.4621125123532)
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:
$$t_{1} = 22.1136379067686$$
$$t_{2} = 31.5384158674614$$
$$t_{3} = 50.3879717890001$$
$$t_{4} = 72.3791203641287$$
$$t_{5} = 100.653454246437$$
$$t_{6} = 37.821601174641$$
$$t_{7} = 56.6711570961797$$
$$t_{8} = -7.63561646197875$$
$$t_{9} = 97.511861592847$$
$$t_{10} = 94.3702689392572$$
$$t_{11} = -39.0688140733743$$
$$t_{12} = 9.54726476204874$$
$$t_{13} = 59.8127497497695$$
$$t_{14} = -23.3608507566309$$
$$t_{15} = 34.6800085210512$$
$$t_{16} = 88.0870836320776$$
$$t_{17} = -19.4338528652826$$
$$t_{18} = -11.5836856349292$$
$$t_{19} = 6.4056966162943$$
$$t_{20} = 28.3968232138706$$
$$t_{21} = -31.2148324394912$$
$$t_{22} = -27.2878416357148$$
$$t_{23} = 0.123351471449465$$
$$t_{24} = 53.5295644425899$$
$$t_{25} = 78.6623056713083$$
$$t_{26} = -35.1418232563624$$
$$t_{27} = 66.0959350569491$$
$$t_{28} = -15.5068952914144$$
$$t_{29} = 75.5207130177185$$
$$t_{30} = 15.8304526025542$$
$$t_{31} = 81.8038983248981$$
$$t_{32} = 44.1047864818205$$
$$t_{33} = 12.6888596750542$$
Puntos máximos de la función:
$$t_{33} = 29.9676195406663$$
$$t_{33} = 45.6755828086154$$
$$t_{33} = 77.0915093445134$$
$$t_{33} = 14.2596562316776$$
$$t_{33} = 64.5251387301542$$
$$t_{33} = 67.666731383744$$
$$t_{33} = -33.1783278478226$$
$$t_{33} = 231.029549370413$$
$$t_{33} = 36.2508048478461$$
$$t_{33} = -25.3243462519939$$
$$t_{33} = 95.9410652660521$$
$$t_{33} = -29.2513370331717$$
$$t_{33} = -13.5440223795782$$
$$t_{33} = 86.5162873052827$$
$$t_{33} = 80.2331019981032$$
$$t_{33} = 58.2419534229746$$
$$t_{33} = -9.62753408038416$$
$$t_{33} = 253.020697945542$$
$$t_{33} = 42.5339901550256$$
$$t_{33} = 1.6946360179382$$
$$t_{33} = -5.01188415768002$$
$$t_{33} = -1.45978595831549$$
$$t_{33} = 73.9499166909236$$
$$t_{33} = 51.958768115795$$
$$t_{33} = 89.6578799588725$$
$$t_{33} = 20.5428415804029$$
$$t_{33} = -37.1053186648767$$
$$t_{33} = 23.6844342334812$$
$$t_{33} = 7.97646933662247$$
$$t_{33} = -17.4703441920742$$
$$t_{33} = -21.3973541839018$$
$$t_{33} = 55.1003607693848$$
Decrece en los intervalos
$$\left[100.653454246437, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -39.0688140733743\right]$$