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$$5 x \cos{\left(x \right)} - 5 \sin{\left(x \right)} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 70.6716857116195$$
$$x_{2} = -48.6741442319544$$
$$x_{3} = 51.8169824872797$$
$$x_{4} = 48.6741442319544$$
$$x_{5} = 17.2207552719308$$
$$x_{6} = -36.1006222443756$$
$$x_{7} = 0$$
$$x_{8} = 45.5311340139913$$
$$x_{9} = 98.9500628243319$$
$$x_{10} = -89.5242209304172$$
$$x_{11} = -4.49340945790906$$
$$x_{12} = -64.3871195905574$$
$$x_{13} = 29.811598790893$$
$$x_{14} = 61.2447302603744$$
$$x_{15} = 39.2444323611642$$
$$x_{16} = 80.0981286289451$$
$$x_{17} = -7.72525183693771$$
$$x_{18} = -20.3713029592876$$
$$x_{19} = -86.3822220347287$$
$$x_{20} = -32.9563890398225$$
$$x_{21} = -10.9041216594289$$
$$x_{22} = -70.6716857116195$$
$$x_{23} = -61.2447302603744$$
$$x_{24} = 92.6661922776228$$
$$x_{25} = -92.6661922776228$$
$$x_{26} = 67.5294347771441$$
$$x_{27} = -14.0661939128315$$
$$x_{28} = 54.9596782878889$$
$$x_{29} = -45.5311340139913$$
$$x_{30} = -39.2444323611642$$
$$x_{31} = 89.5242209304172$$
$$x_{32} = 86.3822220347287$$
$$x_{33} = 4.49340945790906$$
$$x_{34} = -42.3879135681319$$
$$x_{35} = 58.1022547544956$$
$$x_{36} = -23.519452498689$$
$$x_{37} = 36.1006222443756$$
$$x_{38} = -80.0981286289451$$
$$x_{39} = 7.72525183693771$$
$$x_{40} = -76.9560263103312$$
$$x_{41} = 73.8138806006806$$
$$x_{42} = -98.9500628243319$$
$$x_{43} = 95.8081387868617$$
$$x_{44} = 26.6660542588127$$
$$x_{45} = -17.2207552719308$$
$$x_{46} = -26.6660542588127$$
$$x_{47} = 20.3713029592876$$
$$x_{48} = 102.091966464908$$
$$x_{49} = -54.9596782878889$$
$$x_{50} = -73.8138806006806$$
$$x_{51} = -58.1022547544956$$
$$x_{52} = 23.519452498689$$
$$x_{53} = 83.2401924707234$$
$$x_{54} = -95.8081387868617$$
$$x_{55} = -29.811598790893$$
$$x_{56} = -51.8169824872797$$
$$x_{57} = 10.9041216594289$$
$$x_{58} = 14.0661939128315$$
$$x_{59} = 32.9563890398225$$
$$x_{60} = 64.3871195905574$$
$$x_{61} = -67.5294347771441$$
$$x_{62} = 76.9560263103312$$
$$x_{63} = -83.2401924707234$$
$$x_{64} = 42.3879135681319$$
Signos de extremos en los puntos:
(70.6716857116195, 353.464544243924)
(-48.674144231954386, -243.524779982621)
(51.81698248727967, 259.22963017313)
(48.674144231954386, -243.524779982621)
(17.22075527193077, -86.5386868495239)
(-36.10062224437561, -180.710797488168)
(0, 10)
(45.53113401399128, 227.820359424951)
(98.95006282433188, -494.826106704724)
(-89.52422093041719, 447.704876507814)
(-4.493409457909064, -24.1028623848146)
(-64.38711959055742, 322.052069172218)
(29.81159879089296, -149.309456030408)
(61.2447302603744, -306.346097216712)
(39.24443236116419, 196.41322003791)
(80.09812862894512, -400.584272210672)
(-7.725251836937707, 39.5904016050931)
(-20.37130295928756, 102.224310729287)
(-86.38222203472871, -431.997928746584)
(-32.956389039822476, 165.009431427628)
(-10.904121659428899, -55.2060253632466)
(-70.6716857116195, 353.464544243924)
(-61.2447302603744, -306.346097216712)
(92.66619227762284, -463.41189312734)
(-92.66619227762284, -463.41189312734)
(67.52943477714412, -337.758226419429)
(-14.066193912831473, 70.8630439495984)
(54.959678287888934, -274.93483630046)
(-45.53113401399128, 227.820359424951)
(-39.24443236116419, 196.41322003791)
(89.52422093041719, 447.704876507814)
(86.38222203472871, -431.997928746584)
(4.493409457909064, -24.1028623848146)
(-42.38791356813192, -212.116464054235)
(58.10225475449559, 290.640340613977)
(-23.519452498689006, -117.91590757357)
(36.10062224437561, -180.710797488168)
(-80.09812862894512, -400.584272210672)
(7.725251836937707, 39.5904016050931)
(-76.95602631033118, 384.877582950189)
(73.81388060068065, -369.17100213976)
(-98.95006282433188, -494.826106704724)
(95.8081387868617, 479.118971830918)
(26.666054258812675, 133.61136310898)
(-17.22075527193077, -86.5386868495239)
(-26.666054258812675, 133.61136310898)
(20.37130295928756, 102.224310729287)
(102.09196646490764, 510.533292562944)
(-54.959678287888934, -274.93483630046)
(-73.81388060068065, -369.17100213976)
(-58.10225475449559, 290.640340613977)
(23.519452498689006, -117.91590757357)
(83.2401924707234, 416.291057640705)
(-95.8081387868617, 479.118971830918)
(-29.81159879089296, -149.309456030408)
(-51.81698248727967, 259.22963017313)
(10.904121659428899, -55.2060253632466)
(14.066193912831473, 70.8630439495984)
(32.956389039822476, 165.009431427628)
(64.38711959055742, 322.052069172218)
(-67.52943477714412, -337.758226419429)
(76.95602631033118, 384.877582950189)
(-83.2401924707234, 416.291057640705)
(42.38791356813192, -212.116464054235)
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:
$$x_{1} = -48.6741442319544$$
$$x_{2} = 48.6741442319544$$
$$x_{3} = 17.2207552719308$$
$$x_{4} = -36.1006222443756$$
$$x_{5} = 98.9500628243319$$
$$x_{6} = -4.49340945790906$$
$$x_{7} = 29.811598790893$$
$$x_{8} = 61.2447302603744$$
$$x_{9} = 80.0981286289451$$
$$x_{10} = -86.3822220347287$$
$$x_{11} = -10.9041216594289$$
$$x_{12} = -61.2447302603744$$
$$x_{13} = 92.6661922776228$$
$$x_{14} = -92.6661922776228$$
$$x_{15} = 67.5294347771441$$
$$x_{16} = 54.9596782878889$$
$$x_{17} = 86.3822220347287$$
$$x_{18} = 4.49340945790906$$
$$x_{19} = -42.3879135681319$$
$$x_{20} = -23.519452498689$$
$$x_{21} = 36.1006222443756$$
$$x_{22} = -80.0981286289451$$
$$x_{23} = 73.8138806006806$$
$$x_{24} = -98.9500628243319$$
$$x_{25} = -17.2207552719308$$
$$x_{26} = -54.9596782878889$$
$$x_{27} = -73.8138806006806$$
$$x_{28} = 23.519452498689$$
$$x_{29} = -29.811598790893$$
$$x_{30} = 10.9041216594289$$
$$x_{31} = -67.5294347771441$$
$$x_{32} = 42.3879135681319$$
Puntos máximos de la función:
$$x_{32} = 70.6716857116195$$
$$x_{32} = 51.8169824872797$$
$$x_{32} = 45.5311340139913$$
$$x_{32} = -89.5242209304172$$
$$x_{32} = -64.3871195905574$$
$$x_{32} = 39.2444323611642$$
$$x_{32} = -7.72525183693771$$
$$x_{32} = -20.3713029592876$$
$$x_{32} = -32.9563890398225$$
$$x_{32} = -70.6716857116195$$
$$x_{32} = -14.0661939128315$$
$$x_{32} = -45.5311340139913$$
$$x_{32} = -39.2444323611642$$
$$x_{32} = 89.5242209304172$$
$$x_{32} = 58.1022547544956$$
$$x_{32} = 7.72525183693771$$
$$x_{32} = -76.9560263103312$$
$$x_{32} = 95.8081387868617$$
$$x_{32} = 26.6660542588127$$
$$x_{32} = -26.6660542588127$$
$$x_{32} = 20.3713029592876$$
$$x_{32} = 102.091966464908$$
$$x_{32} = -58.1022547544956$$
$$x_{32} = 83.2401924707234$$
$$x_{32} = -95.8081387868617$$
$$x_{32} = -51.8169824872797$$
$$x_{32} = 14.0661939128315$$
$$x_{32} = 32.9563890398225$$
$$x_{32} = 64.3871195905574$$
$$x_{32} = 76.9560263103312$$
$$x_{32} = -83.2401924707234$$
Decrece en los intervalos
$$\left[98.9500628243319, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -98.9500628243319\right]$$