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$$- \frac{x \sin{\left(x \right)}}{\cos{\left(x \right)}} + \log{\left(\cos{\left(x \right)} \right)} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 31.4159265358979$$
$$x_{2} = -12.5663706143592$$
$$x_{3} = 75.398223686155$$
$$x_{4} = -69.1150383789755$$
$$x_{5} = -50.2654824574367$$
$$x_{6} = -56.5486677646163$$
$$x_{7} = 69.1150383789755$$
$$x_{8} = -62.8318530717959$$
$$x_{9} = -6.28318530717959$$
$$x_{10} = 6.28318530717959$$
$$x_{11} = 62.8318530717959$$
$$x_{12} = -25.1327412287183$$
$$x_{13} = 94.2477796076938$$
$$x_{14} = -37.6991118430775$$
$$x_{15} = -100.530964914873$$
$$x_{16} = -43.9822971502571$$
$$x_{17} = 25.1327412287183$$
$$x_{18} = 87.9645943005142$$
$$x_{19} = 43.9822971502571$$
$$x_{20} = -31.4159265358979$$
$$x_{21} = -94.2477796076938$$
$$x_{22} = 18.8495559215388$$
$$x_{23} = -18.8495559215388$$
$$x_{24} = 12.5663706143592$$
$$x_{25} = 81.6814089933346$$
$$x_{26} = -75.398223686155$$
$$x_{27} = -81.6814089933346$$
$$x_{28} = 50.2654824574367$$
$$x_{29} = -87.9645943005142$$
$$x_{30} = 56.5486677646163$$
$$x_{31} = 37.6991118430775$$
$$x_{32} = 100.530964914873$$
$$x_{33} = 0$$
Signos de extremos en los puntos:
(31.41592653589793, 0)
(-12.566370614359172, 0)
(75.39822368615503, 0)
(-69.11503837897546, 0)
(-50.26548245743669, 0)
(-56.548667764616276, 0)
(69.11503837897546, 0)
(-62.83185307179586, 0)
(-6.283185307179586, 0)
(6.283185307179586, 0)
(62.83185307179586, 0)
(-25.132741228718345, 0)
(94.2477796076938, 0)
(-37.69911184307752, 0)
(-100.53096491487338, 0)
(-43.982297150257104, 0)
(25.132741228718345, 0)
(87.96459430051421, 0)
(43.982297150257104, 0)
(-31.41592653589793, 0)
(-94.2477796076938, 0)
(18.84955592153876, 0)
(-18.84955592153876, 0)
(12.566370614359172, 0)
(81.68140899333463, 0)
(-75.39822368615503, 0)
(-81.68140899333463, 0)
(50.26548245743669, 0)
(-87.96459430051421, 0)
(56.548667764616276, 0)
(37.69911184307752, 0)
(100.53096491487338, 0)
(0, 0)
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:
$$x_{1} = -12.5663706143592$$
$$x_{2} = -69.1150383789755$$
$$x_{3} = -50.2654824574367$$
$$x_{4} = -56.5486677646163$$
$$x_{5} = -62.8318530717959$$
$$x_{6} = -6.28318530717959$$
$$x_{7} = -25.1327412287183$$
$$x_{8} = -37.6991118430775$$
$$x_{9} = -100.530964914873$$
$$x_{10} = -43.9822971502571$$
$$x_{11} = -31.4159265358979$$
$$x_{12} = -94.2477796076938$$
$$x_{13} = -18.8495559215388$$
$$x_{14} = -75.398223686155$$
$$x_{15} = -81.6814089933346$$
$$x_{16} = -87.9645943005142$$
Puntos máximos de la función:
$$x_{16} = 31.4159265358979$$
$$x_{16} = 75.398223686155$$
$$x_{16} = 69.1150383789755$$
$$x_{16} = 6.28318530717959$$
$$x_{16} = 62.8318530717959$$
$$x_{16} = 94.2477796076938$$
$$x_{16} = 25.1327412287183$$
$$x_{16} = 87.9645943005142$$
$$x_{16} = 43.9822971502571$$
$$x_{16} = 18.8495559215388$$
$$x_{16} = 12.5663706143592$$
$$x_{16} = 81.6814089933346$$
$$x_{16} = 50.2654824574367$$
$$x_{16} = 56.5486677646163$$
$$x_{16} = 37.6991118430775$$
$$x_{16} = 100.530964914873$$
Decrece en los intervalos
$$\left[-6.28318530717959, 6.28318530717959\right]$$
Crece en los intervalos
$$\left(-\infty, -100.530964914873\right]$$