Sr Examen

Gráfico de la función y = cosx-logcosx/loge

v

Gráfico:

interior superior

Puntos de intersección:

mostrar?

Definida a trozos:

Solución

Ha introducido [src]
                log(cos(x))*x
f(x) = cos(x) - -------------
                    log(E)   
f(x)=xlog(cos(x))log(e)+cos(x)f{\left(x \right)} = - \frac{x \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} + \cos{\left(x \right)}
f = -x*log(cos(x))/log(E) + cos(x)
Gráfico de la función
02468-8-6-4-2-1010-5050
Puntos de cruce con el eje de coordenadas X
El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
xlog(cos(x))log(e)+cos(x)=0- \frac{x \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} + \cos{\left(x \right)} = 0
Resolvermos esta ecuación
Puntos de cruce con el eje X:

Solución numérica
x1=0.974252590832371x_{1} = -0.974252590832371
x2=43.771701843272x_{2} = -43.771701843272
x3=37.9248530626587x_{3} = -37.9248530626587
x4=75.2366011570112x_{4} = -75.2366011570112
x5=37.4720566767852x_{5} = -37.4720566767852
x6=87.8148084868011x_{6} = -87.8148084868011
x7=88.1141292605797x_{7} = -88.1141292605797
x8=18.5320847825305x_{8} = -18.5320847825305
x9=44.1919178554852x_{9} = -44.1919178554852
x10=31.1678106093423x_{10} = -31.1678106093423
x11=100.390744190501x_{11} = -100.390744190501
x12=6.78128200472309x_{12} = -6.78128200472309
x13=62.6550509842081x_{13} = -62.6550509842081
x14=56.7342668969425x_{14} = -56.7342668969425
x15=81.5260423202257x_{15} = -81.5260423202257
x16=50.0682118001178x_{16} = -50.0682118001178
x17=94.1030129922823x_{17} = -94.1030129922823
x18=68.9463367882632x_{18} = -68.9463367882632
x19=69.283336875353x_{19} = -69.283336875353
x20=25.4063113142057x_{20} = -25.4063113142057
x21=24.8563099344224x_{21} = -24.8563099344224
x22=50.462001535176x_{22} = -50.462001535176
x23=94.392327270775x_{23} = -94.392327270775
x24=56.3624714317283x_{24} = -56.3624714317283
x25=12.9410822311231x_{25} = -12.9410822311231
x26=81.8364853949152x_{26} = -81.8364853949152
x27=12.1812215419484x_{27} = -12.1812215419484
x28=5.74948651604217x_{28} = -5.74948651604217
x29=19.1620991877178x_{29} = -19.1620991877178
x30=31.6621752139336x_{30} = -31.6621752139336
x31=75.5595064479637x_{31} = -75.5595064479637
x32=63.0081692283478x_{32} = -63.0081692283478
Puntos de cruce con el eje de coordenadas Y
El gráfico cruce el eje Y cuando x es igual a 0:
sustituimos x = 0 en cos(x) - log(cos(x))*x/log(E).
0log(cos(0))log(e)+cos(0)- \frac{0 \log{\left(\cos{\left(0 \right)} \right)}}{\log{\left(e \right)}} + \cos{\left(0 \right)}
Resultado:
f(0)=1f{\left(0 \right)} = 1
Punto:
(0, 1)
Extremos de la función
Para hallar los extremos hay que resolver la ecuación
ddxf(x)=0\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:
ddxf(x)=\frac{d}{d x} f{\left(x \right)} =
primera derivada
xsin(x)cos(x)log(cos(x))log(e)sin(x)=0\frac{\frac{x \sin{\left(x \right)}}{\cos{\left(x \right)}} - \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} - \sin{\left(x \right)} = 0
Resolvermos esta ecuación
Raíces de esta ecuación
x1=31.4159265358979x_{1} = 31.4159265358979
x2=12.5663706143592x_{2} = -12.5663706143592
x3=75.398223686155x_{3} = 75.398223686155
x4=69.1150383789755x_{4} = -69.1150383789755
x5=50.2654824574367x_{5} = -50.2654824574367
x6=56.5486677646163x_{6} = -56.5486677646163
x7=69.1150383789755x_{7} = 69.1150383789755
x8=62.8318530717959x_{8} = -62.8318530717959
x9=6.28318530717959x_{9} = -6.28318530717959
x10=37.6991118430775x_{10} = 37.6991118430775
x11=6.28318530717959x_{11} = 6.28318530717959
x12=62.8318530717959x_{12} = 62.8318530717959
x13=81.6814089933346x_{13} = 81.6814089933346
x14=25.1327412287183x_{14} = -25.1327412287183
x15=94.2477796076938x_{15} = 94.2477796076938
x16=37.6991118430775x_{16} = -37.6991118430775
x17=100.530964914873x_{17} = -100.530964914873
x18=43.9822971502571x_{18} = -43.9822971502571
x19=25.1327412287183x_{19} = 25.1327412287183
x20=87.9645943005142x_{20} = 87.9645943005142
x21=43.9822971502571x_{21} = 43.9822971502571
x22=100.530964914873x_{22} = 100.530964914873
x23=94.2477796076938x_{23} = -94.2477796076938
x24=31.4159265358979x_{24} = -31.4159265358979
x25=18.8495559215388x_{25} = 18.8495559215388
x26=18.8495559215388x_{26} = -18.8495559215388
x27=12.5663706143592x_{27} = 12.5663706143592
x28=75.398223686155x_{28} = -75.398223686155
x29=81.6814089933346x_{29} = -81.6814089933346
x30=50.2654824574367x_{30} = 50.2654824574367
x31=87.9645943005142x_{31} = -87.9645943005142
x32=56.5486677646163x_{32} = 56.5486677646163
x33=0x_{33} = 0
Signos de extremos en los puntos:
(31.41592653589793, 1)

(-12.566370614359172, 1)

(75.39822368615503, 1)

(-69.11503837897546, 1)

(-50.26548245743669, 1)

(-56.548667764616276, 1)

(69.11503837897546, 1)

(-62.83185307179586, 1)

(-6.283185307179586, 1)

(37.69911184307752, 1)

(6.283185307179586, 1)

(62.83185307179586, 1)

(81.68140899333463, 1)

(-25.132741228718345, 1)

(94.2477796076938, 1)

(-37.69911184307752, 1)

(-100.53096491487338, 1)

(-43.982297150257104, 1)

(25.132741228718345, 1)

(87.96459430051421, 1)

(43.982297150257104, 1)

(100.53096491487338, 1)

(-94.2477796076938, 1)

(-31.41592653589793, 1)

(18.84955592153876, 1)

(-18.84955592153876, 1)

(12.566370614359172, 1)

(-75.39822368615503, 1)

(-81.68140899333463, 1)

(50.26548245743669, 1)

(-87.96459430051421, 1)

(56.548667764616276, 1)

(0, 1)


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:
x1=31.4159265358979x_{1} = 31.4159265358979
x2=75.398223686155x_{2} = 75.398223686155
x3=69.1150383789755x_{3} = 69.1150383789755
x4=37.6991118430775x_{4} = 37.6991118430775
x5=6.28318530717959x_{5} = 6.28318530717959
x6=62.8318530717959x_{6} = 62.8318530717959
x7=81.6814089933346x_{7} = 81.6814089933346
x8=94.2477796076938x_{8} = 94.2477796076938
x9=25.1327412287183x_{9} = 25.1327412287183
x10=87.9645943005142x_{10} = 87.9645943005142
x11=43.9822971502571x_{11} = 43.9822971502571
x12=100.530964914873x_{12} = 100.530964914873
x13=18.8495559215388x_{13} = 18.8495559215388
x14=12.5663706143592x_{14} = 12.5663706143592
x15=50.2654824574367x_{15} = 50.2654824574367
x16=56.5486677646163x_{16} = 56.5486677646163
Puntos máximos de la función:
x16=12.5663706143592x_{16} = -12.5663706143592
x16=69.1150383789755x_{16} = -69.1150383789755
x16=50.2654824574367x_{16} = -50.2654824574367
x16=56.5486677646163x_{16} = -56.5486677646163
x16=62.8318530717959x_{16} = -62.8318530717959
x16=6.28318530717959x_{16} = -6.28318530717959
x16=25.1327412287183x_{16} = -25.1327412287183
x16=37.6991118430775x_{16} = -37.6991118430775
x16=100.530964914873x_{16} = -100.530964914873
x16=43.9822971502571x_{16} = -43.9822971502571
x16=94.2477796076938x_{16} = -94.2477796076938
x16=31.4159265358979x_{16} = -31.4159265358979
x16=18.8495559215388x_{16} = -18.8495559215388
x16=75.398223686155x_{16} = -75.398223686155
x16=81.6814089933346x_{16} = -81.6814089933346
x16=87.9645943005142x_{16} = -87.9645943005142
x16=0x_{16} = 0
Decrece en los intervalos
[100.530964914873,)\left[100.530964914873, \infty\right)
Crece en los intervalos
[0,6.28318530717959]\left[0, 6.28318530717959\right]
Puntos de flexiones
Hallemos los puntos de flexiones, para eso hay que resolver la ecuación
d2dx2f(x)=0\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0
(la segunda derivada es igual a cero),
las raíces de la ecuación obtenida serán los puntos de flexión para el gráfico de la función indicado:
d2dx2f(x)=\frac{d^{2}}{d x^{2}} f{\left(x \right)} =
segunda derivada
xsin2(x)cos2(x)+x+2sin(x)cos(x)log(e)cos(x)=0\frac{\frac{x \sin^{2}{\left(x \right)}}{\cos^{2}{\left(x \right)}} + x + \frac{2 \sin{\left(x \right)}}{\cos{\left(x \right)}}}{\log{\left(e \right)}} - \cos{\left(x \right)} = 0
Resolvermos esta ecuación
Raíces de esta ecuación
x1=0.302099169447253x_{1} = 0.302099169447253

Intervalos de convexidad y concavidad:
Hallemos los intervales donde la función es convexa o cóncava, para eso veamos cómo se comporta la función en los puntos de flexiones:
Cóncava en los intervalos
[0.302099169447253,)\left[0.302099169447253, \infty\right)
Convexa en los intervalos
(,0.302099169447253]\left(-\infty, 0.302099169447253\right]
Asíntotas horizontales
Hallemos las asíntotas horizontales mediante los límites de esta función con x->+oo y x->-oo
limx(xlog(cos(x))log(e)+cos(x))=log(1,1)\lim_{x \to -\infty}\left(- \frac{x \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} + \cos{\left(x \right)}\right) = \infty \log{\left(\left\langle -1, 1\right\rangle \right)}
Tomamos como el límite
es decir,
ecuación de la asíntota horizontal a la izquierda:
y=log(1,1)y = \infty \log{\left(\left\langle -1, 1\right\rangle \right)}
limx(xlog(cos(x))log(e)+cos(x))=1,1log(1,1)\lim_{x \to \infty}\left(- \frac{x \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} + \cos{\left(x \right)}\right) = \left\langle -1, 1\right\rangle - \infty \log{\left(\left\langle -1, 1\right\rangle \right)}
Tomamos como el límite
es decir,
ecuación de la asíntota horizontal a la derecha:
y=1,1log(1,1)y = \left\langle -1, 1\right\rangle - \infty \log{\left(\left\langle -1, 1\right\rangle \right)}
Asíntotas inclinadas
Se puede hallar la asíntota inclinada calculando el límite de la función cos(x) - log(cos(x))*x/log(E), dividida por x con x->+oo y x ->-oo
True

Tomamos como el límite
es decir,
ecuación de la asíntota inclinada a la izquierda:
y=xlimx(xlog(cos(x))log(e)+cos(x)x)y = x \lim_{x \to -\infty}\left(\frac{- \frac{x \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} + \cos{\left(x \right)}}{x}\right)
limx(xlog(cos(x))log(e)+cos(x)x)=0\lim_{x \to \infty}\left(\frac{- \frac{x \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} + \cos{\left(x \right)}}{x}\right) = 0
Tomamos como el límite
es decir,
la inclinada coincide con la asíntota horizontal a la izquierda
Paridad e imparidad de la función
Comprobemos si la función es par o impar mediante las relaciones f = f(-x) и f = -f(-x).
Pues, comprobamos:
xlog(cos(x))log(e)+cos(x)=xlog(cos(x))log(e)+cos(x)- \frac{x \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} + \cos{\left(x \right)} = \frac{x \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} + \cos{\left(x \right)}
- No
xlog(cos(x))log(e)+cos(x)=xlog(cos(x))log(e)cos(x)- \frac{x \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} + \cos{\left(x \right)} = - \frac{x \log{\left(\cos{\left(x \right)} \right)}}{\log{\left(e \right)}} - \cos{\left(x \right)}
- No
es decir, función
no es
par ni impar