Sr Examen

Gráfico de la función y = cos((|x|))

v

Gráfico:

interior superior

Puntos de intersección:

mostrar?

Definida a trozos:

Solución

Ha introducido [src]
f(x) = cos(|x|)
f(x)=cos(x)f{\left(x \right)} = \cos{\left(\left|{x}\right| \right)}
f = cos(|x|)
Gráfico de la función
02468-8-6-4-2-10102-2
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:
cos(x)=0\cos{\left(\left|{x}\right| \right)} = 0
Resolvermos esta ecuación
Puntos de cruce con el eje X:

Solución analítica
x1=π2x_{1} = \frac{\pi}{2}
x2=3π2x_{2} = \frac{3 \pi}{2}
Solución numérica
x1=14.1371669411541x_{1} = 14.1371669411541
x2=73.8274273593601x_{2} = 73.8274273593601
x3=92.6769832808989x_{3} = -92.6769832808989
x4=48.6946861306418x_{4} = -48.6946861306418
x5=89.5353906273091x_{5} = 89.5353906273091
x6=2266.65909956504x_{6} = -2266.65909956504
x7=23.5619449019235x_{7} = -23.5619449019235
x8=86.3937979737193x_{8} = -86.3937979737193
x9=39.2699081698724x_{9} = 39.2699081698724
x10=17.2787595947439x_{10} = -17.2787595947439
x11=20.4203522483337x_{11} = 20.4203522483337
x12=26.7035375555132x_{12} = -26.7035375555132
x13=61.261056745001x_{13} = 61.261056745001
x14=42.4115008234622x_{14} = 42.4115008234622
x15=64.4026493985908x_{15} = -64.4026493985908
x16=83.2522053201295x_{16} = -83.2522053201295
x17=4.71238898038469x_{17} = -4.71238898038469
x18=168.075206967054x_{18} = -168.075206967054
x19=42.4115008234622x_{19} = -42.4115008234622
x20=29.845130209103x_{20} = -29.845130209103
x21=17.2787595947439x_{21} = 17.2787595947439
x22=51.8362787842316x_{22} = 51.8362787842316
x23=1.5707963267949x_{23} = 1.5707963267949
x24=67.5442420521806x_{24} = -67.5442420521806
x25=36.1283155162826x_{25} = -36.1283155162826
x26=45.553093477052x_{26} = 45.553093477052
x27=80.1106126665397x_{27} = -80.1106126665397
x28=86.3937979737193x_{28} = 86.3937979737193
x29=73.8274273593601x_{29} = -73.8274273593601
x30=32.9867228626928x_{30} = 32.9867228626928
x31=64.4026493985908x_{31} = 64.4026493985908
x32=1.5707963267949x_{32} = -1.5707963267949
x33=95.8185759344887x_{33} = 95.8185759344887
x34=20.4203522483337x_{34} = -20.4203522483337
x35=10.9955742875643x_{35} = -10.9955742875643
x36=98.9601685880785x_{36} = -98.9601685880785
x37=92.6769832808989x_{37} = 92.6769832808989
x38=36.1283155162826x_{38} = 36.1283155162826
x39=32.9867228626928x_{39} = -32.9867228626928
x40=39.2699081698724x_{40} = -39.2699081698724
x41=58.1194640914112x_{41} = -58.1194640914112
x42=61.261056745001x_{42} = -61.261056745001
x43=4.71238898038469x_{43} = 4.71238898038469
x44=76.9690200129499x_{44} = -76.9690200129499
x45=95.8185759344887x_{45} = -95.8185759344887
x46=48.6946861306418x_{46} = 48.6946861306418
x47=51.8362787842316x_{47} = -51.8362787842316
x48=23.5619449019235x_{48} = 23.5619449019235
x49=67.5442420521806x_{49} = 67.5442420521806
x50=14.1371669411541x_{50} = -14.1371669411541
x51=76.9690200129499x_{51} = 76.9690200129499
x52=98.9601685880785x_{52} = 98.9601685880785
x53=80.1106126665397x_{53} = 80.1106126665397
x54=7.85398163397448x_{54} = -7.85398163397448
x55=7.85398163397448x_{55} = 7.85398163397448
x56=387.986692718339x_{56} = -387.986692718339
x57=58.1194640914112x_{57} = 58.1194640914112
x58=45.553093477052x_{58} = -45.553093477052
x59=83.2522053201295x_{59} = 83.2522053201295
x60=54.9778714378214x_{60} = 54.9778714378214
x61=26.7035375555132x_{61} = 26.7035375555132
x62=89.5353906273091x_{62} = -89.5353906273091
x63=10.9955742875643x_{63} = 10.9955742875643
x64=70.6858347057703x_{64} = -70.6858347057703
x65=70.6858347057703x_{65} = 70.6858347057703
x66=54.9778714378214x_{66} = -54.9778714378214
x67=29.845130209103x_{67} = 29.845130209103
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|).
cos(0)\cos{\left(\left|{0}\right| \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
sin(x)sign(x)=0- \sin{\left(\left|{x}\right| \right)} \operatorname{sign}{\left(x \right)} = 0
Resolvermos esta ecuación
Raíces de esta ecuación
x1=40.8407044966673x_{1} = 40.8407044966673
x2=267.035375555132x_{2} = -267.035375555132
x3=0x_{3} = 0
x4=18.8495559215388x_{4} = -18.8495559215388
x5=56.5486677646163x_{5} = -56.5486677646163
x6=97.3893722612836x_{6} = 97.3893722612836
x7=34.5575191894877x_{7} = 34.5575191894877
x8=53.4070751110265x_{8} = 53.4070751110265
x9=47.1238898038469x_{9} = 47.1238898038469
x10=97.3893722612836x_{10} = -97.3893722612836
x11=62.8318530717959x_{11} = 62.8318530717959
x12=87.9645943005142x_{12} = 87.9645943005142
x13=43.9822971502571x_{13} = 43.9822971502571
x14=37.6991118430775x_{14} = 37.6991118430775
x15=21.9911485751286x_{15} = -21.9911485751286
x16=3.14159265358979x_{16} = 3.14159265358979
x17=69.1150383789755x_{17} = 69.1150383789755
x18=65.9734457253857x_{18} = 65.9734457253857
x19=50.2654824574367x_{19} = -50.2654824574367
x20=94.2477796076938x_{20} = -94.2477796076938
x21=2642.07942166902x_{21} = -2642.07942166902
x22=75.398223686155x_{22} = -75.398223686155
x23=53.4070751110265x_{23} = -53.4070751110265
x24=12.5663706143592x_{24} = 12.5663706143592
x25=9.42477796076938x_{25} = -9.42477796076938
x26=113.097335529233x_{26} = -113.097335529233
x27=34.5575191894877x_{27} = -34.5575191894877
x28=21.9911485751286x_{28} = 21.9911485751286
x29=47.1238898038469x_{29} = -47.1238898038469
x30=43.9822971502571x_{30} = -43.9822971502571
x31=28.2743338823081x_{31} = 28.2743338823081
x32=31.4159265358979x_{32} = -31.4159265358979
x33=3.14159265358979x_{33} = -3.14159265358979
x34=6.28318530717959x_{34} = -6.28318530717959
x35=25.1327412287183x_{35} = -25.1327412287183
x36=62.8318530717959x_{36} = -62.8318530717959
x37=31.4159265358979x_{37} = 31.4159265358979
x38=65.9734457253857x_{38} = -65.9734457253857
x39=72.2566310325652x_{39} = 72.2566310325652
x40=59.6902604182061x_{40} = -59.6902604182061
x41=94.2477796076938x_{41} = 94.2477796076938
x42=81.6814089933346x_{42} = 81.6814089933346
x43=91.106186954104x_{43} = -91.106186954104
x44=100.530964914873x_{44} = -100.530964914873
x45=59.6902604182061x_{45} = 59.6902604182061
x46=40.8407044966673x_{46} = -40.8407044966673
x47=91.106186954104x_{47} = 91.106186954104
x48=78.5398163397448x_{48} = 78.5398163397448
x49=12.5663706143592x_{49} = -12.5663706143592
x50=56.5486677646163x_{50} = 56.5486677646163
x51=84.8230016469244x_{51} = 84.8230016469244
x52=100.530964914873x_{52} = 100.530964914873
x53=69.1150383789755x_{53} = -69.1150383789755
x54=9.42477796076938x_{54} = 9.42477796076938
x55=84.8230016469244x_{55} = -84.8230016469244
x56=78.5398163397448x_{56} = -78.5398163397448
x57=87.9645943005142x_{57} = -87.9645943005142
x58=81.6814089933346x_{58} = -81.6814089933346
x59=15.707963267949x_{59} = 15.707963267949
x60=28.2743338823081x_{60} = -28.2743338823081
x61=15.707963267949x_{61} = -15.707963267949
x62=37.6991118430775x_{62} = -37.6991118430775
x63=18.8495559215388x_{63} = 18.8495559215388
x64=25.1327412287183x_{64} = 25.1327412287183
x65=50.2654824574367x_{65} = 50.2654824574367
x66=72.2566310325652x_{66} = -72.2566310325652
x67=75.398223686155x_{67} = 75.398223686155
x68=232.477856365645x_{68} = -232.477856365645
x69=6.28318530717959x_{69} = 6.28318530717959
Signos de extremos en los puntos:
(40.840704496667314, -1)

(-267.0353755551324, -1)

(0, 1)

(-18.84955592153876, 1)

(-56.548667764616276, 1)

(97.3893722612836, -1)

(34.55751918948773, -1)

(53.40707511102649, -1)

(47.1238898038469, -1)

(-97.3893722612836, -1)

(62.83185307179586, 1)

(87.96459430051421, 1)

(43.982297150257104, 1)

(37.69911184307752, 1)

(-21.991148575128552, -1)

(3.141592653589793, -1)

(69.11503837897546, 1)

(65.97344572538566, -1)

(-50.26548245743669, 1)

(-94.2477796076938, 1)

(-2642.079421669016, -1)

(-75.39822368615503, 1)

(-53.40707511102649, -1)

(12.566370614359172, 1)

(-9.42477796076938, -1)

(-113.09733552923255, 1)

(-34.55751918948773, -1)

(21.991148575128552, -1)

(-47.1238898038469, -1)

(-43.982297150257104, 1)

(28.274333882308138, -1)

(-31.41592653589793, 1)

(-3.141592653589793, -1)

(-6.283185307179586, 1)

(-25.132741228718345, 1)

(-62.83185307179586, 1)

(31.41592653589793, 1)

(-65.97344572538566, -1)

(72.25663103256524, -1)

(-59.69026041820607, -1)

(94.2477796076938, 1)

(81.68140899333463, 1)

(-91.106186954104, -1)

(-100.53096491487338, 1)

(59.69026041820607, -1)

(-40.840704496667314, -1)

(91.106186954104, -1)

(78.53981633974483, -1)

(-12.566370614359172, 1)

(56.548667764616276, 1)

(84.82300164692441, -1)

(100.53096491487338, 1)

(-69.11503837897546, 1)

(9.42477796076938, -1)

(-84.82300164692441, -1)

(-78.53981633974483, -1)

(-87.96459430051421, 1)

(-81.68140899333463, 1)

(15.707963267948966, -1)

(-28.274333882308138, -1)

(-15.707963267948966, -1)

(-37.69911184307752, 1)

(18.84955592153876, 1)

(25.132741228718345, 1)

(50.26548245743669, 1)

(-72.25663103256524, -1)

(75.39822368615503, 1)

(-232.4778563656447, 1)

(6.283185307179586, 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=40.8407044966673x_{1} = 40.8407044966673
x2=267.035375555132x_{2} = -267.035375555132
x3=97.3893722612836x_{3} = 97.3893722612836
x4=34.5575191894877x_{4} = 34.5575191894877
x5=53.4070751110265x_{5} = 53.4070751110265
x6=47.1238898038469x_{6} = 47.1238898038469
x7=97.3893722612836x_{7} = -97.3893722612836
x8=21.9911485751286x_{8} = -21.9911485751286
x9=3.14159265358979x_{9} = 3.14159265358979
x10=65.9734457253857x_{10} = 65.9734457253857
x11=2642.07942166902x_{11} = -2642.07942166902
x12=53.4070751110265x_{12} = -53.4070751110265
x13=9.42477796076938x_{13} = -9.42477796076938
x14=34.5575191894877x_{14} = -34.5575191894877
x15=21.9911485751286x_{15} = 21.9911485751286
x16=47.1238898038469x_{16} = -47.1238898038469
x17=28.2743338823081x_{17} = 28.2743338823081
x18=3.14159265358979x_{18} = -3.14159265358979
x19=65.9734457253857x_{19} = -65.9734457253857
x20=72.2566310325652x_{20} = 72.2566310325652
x21=59.6902604182061x_{21} = -59.6902604182061
x22=91.106186954104x_{22} = -91.106186954104
x23=59.6902604182061x_{23} = 59.6902604182061
x24=40.8407044966673x_{24} = -40.8407044966673
x25=91.106186954104x_{25} = 91.106186954104
x26=78.5398163397448x_{26} = 78.5398163397448
x27=84.8230016469244x_{27} = 84.8230016469244
x28=9.42477796076938x_{28} = 9.42477796076938
x29=84.8230016469244x_{29} = -84.8230016469244
x30=78.5398163397448x_{30} = -78.5398163397448
x31=15.707963267949x_{31} = 15.707963267949
x32=28.2743338823081x_{32} = -28.2743338823081
x33=15.707963267949x_{33} = -15.707963267949
x34=72.2566310325652x_{34} = -72.2566310325652
Puntos máximos de la función:
x34=0x_{34} = 0
x34=18.8495559215388x_{34} = -18.8495559215388
x34=56.5486677646163x_{34} = -56.5486677646163
x34=62.8318530717959x_{34} = 62.8318530717959
x34=87.9645943005142x_{34} = 87.9645943005142
x34=43.9822971502571x_{34} = 43.9822971502571
x34=37.6991118430775x_{34} = 37.6991118430775
x34=69.1150383789755x_{34} = 69.1150383789755
x34=50.2654824574367x_{34} = -50.2654824574367
x34=94.2477796076938x_{34} = -94.2477796076938
x34=75.398223686155x_{34} = -75.398223686155
x34=12.5663706143592x_{34} = 12.5663706143592
x34=113.097335529233x_{34} = -113.097335529233
x34=43.9822971502571x_{34} = -43.9822971502571
x34=31.4159265358979x_{34} = -31.4159265358979
x34=6.28318530717959x_{34} = -6.28318530717959
x34=25.1327412287183x_{34} = -25.1327412287183
x34=62.8318530717959x_{34} = -62.8318530717959
x34=31.4159265358979x_{34} = 31.4159265358979
x34=94.2477796076938x_{34} = 94.2477796076938
x34=81.6814089933346x_{34} = 81.6814089933346
x34=100.530964914873x_{34} = -100.530964914873
x34=12.5663706143592x_{34} = -12.5663706143592
x34=56.5486677646163x_{34} = 56.5486677646163
x34=100.530964914873x_{34} = 100.530964914873
x34=69.1150383789755x_{34} = -69.1150383789755
x34=87.9645943005142x_{34} = -87.9645943005142
x34=81.6814089933346x_{34} = -81.6814089933346
x34=37.6991118430775x_{34} = -37.6991118430775
x34=18.8495559215388x_{34} = 18.8495559215388
x34=25.1327412287183x_{34} = 25.1327412287183
x34=50.2654824574367x_{34} = 50.2654824574367
x34=75.398223686155x_{34} = 75.398223686155
x34=232.477856365645x_{34} = -232.477856365645
x34=6.28318530717959x_{34} = 6.28318530717959
Decrece en los intervalos
[97.3893722612836,)\left[97.3893722612836, \infty\right)
Crece en los intervalos
(,2642.07942166902]\left(-\infty, -2642.07942166902\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
(2sin(x)δ(x)+cos(x)sign2(x))=0- (2 \sin{\left(\left|{x}\right| \right)} \delta\left(x\right) + \cos{\left(\left|{x}\right| \right)} \operatorname{sign}^{2}{\left(x \right)}) = 0
Resolvermos esta ecuación
Raíces de esta ecuación
x1=π2x_{1} = - \frac{\pi}{2}
x2=π2x_{2} = \frac{\pi}{2}

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
(,π2][π2,)\left(-\infty, - \frac{\pi}{2}\right] \cup \left[\frac{\pi}{2}, \infty\right)
Convexa en los intervalos
[π2,π2]\left[- \frac{\pi}{2}, \frac{\pi}{2}\right]
Asíntotas horizontales
Hallemos las asíntotas horizontales mediante los límites de esta función con x->+oo y x->-oo
limxcos(x)=1,1\lim_{x \to -\infty} \cos{\left(\left|{x}\right| \right)} = \left\langle -1, 1\right\rangle
Tomamos como el límite
es decir,
ecuación de la asíntota horizontal a la izquierda:
y=1,1y = \left\langle -1, 1\right\rangle
limxcos(x)=1,1\lim_{x \to \infty} \cos{\left(\left|{x}\right| \right)} = \left\langle -1, 1\right\rangle
Tomamos como el límite
es decir,
ecuación de la asíntota horizontal a la derecha:
y=1,1y = \left\langle -1, 1\right\rangle
Asíntotas inclinadas
Se puede hallar la asíntota inclinada calculando el límite de la función cos(|x|), dividida por x con x->+oo y x ->-oo
limx(cos(x)x)=0\lim_{x \to -\infty}\left(\frac{\cos{\left(\left|{x}\right| \right)}}{x}\right) = 0
Tomamos como el límite
es decir,
la inclinada coincide con la asíntota horizontal a la derecha
limx(cos(x)x)=0\lim_{x \to \infty}\left(\frac{\cos{\left(\left|{x}\right| \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:
cos(x)=cos(x)\cos{\left(\left|{x}\right| \right)} = \cos{\left(\left|{x}\right| \right)}
- Sí
cos(x)=cos(x)\cos{\left(\left|{x}\right| \right)} = - \cos{\left(\left|{x}\right| \right)}
- No
es decir, función
es
par