Sr Examen

5sinx+cos2x≥-2 desigualdades

En la desigualdad la incógnita

Solución

Ha introducido [src]
5*sin(x) + cos(2*x) >= -2
$$5 \sin{\left(x \right)} + \cos{\left(2 x \right)} \geq -2$$
5*sin(x) + cos(2*x) >= -2
Solución detallada
Se da la desigualdad:
$$5 \sin{\left(x \right)} + \cos{\left(2 x \right)} \geq -2$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$5 \sin{\left(x \right)} + \cos{\left(2 x \right)} = -2$$
Resolvemos:
Tenemos la ecuación
$$5 \sin{\left(x \right)} + \cos{\left(2 x \right)} = -2$$
cambiamos
$$5 \sin{\left(x \right)} + \cos{\left(2 x \right)} + 2 = 0$$
$$- 2 \sin^{2}{\left(x \right)} + 5 \sin{\left(x \right)} + 3 = 0$$
Sustituimos
$$w = \sin{\left(x \right)}$$
Es la ecuación de la forma
a*w^2 + b*w + c = 0

La ecuación cuadrática puede ser resuelta
con la ayuda del discriminante.
Las raíces de la ecuación cuadrática:
$$w_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$w_{2} = \frac{- \sqrt{D} - b}{2 a}$$
donde D = b^2 - 4*a*c es el discriminante.
Como
$$a = -2$$
$$b = 5$$
$$c = 3$$
, entonces
D = b^2 - 4 * a * c = 

(5)^2 - 4 * (-2) * (3) = 49

Como D > 0 la ecuación tiene dos raíces.
w1 = (-b + sqrt(D)) / (2*a)

w2 = (-b - sqrt(D)) / (2*a)

o
$$w_{1} = - \frac{1}{2}$$
$$w_{2} = 3$$
hacemos cambio inverso
$$\sin{\left(x \right)} = w$$
Tenemos la ecuación
$$\sin{\left(x \right)} = w$$
es la ecuación trigonométrica más simple
Esta ecuación se reorganiza en
$$x = 2 \pi n + \operatorname{asin}{\left(w \right)}$$
$$x = 2 \pi n - \operatorname{asin}{\left(w \right)} + \pi$$
O
$$x = 2 \pi n + \operatorname{asin}{\left(w \right)}$$
$$x = 2 \pi n - \operatorname{asin}{\left(w \right)} + \pi$$
, donde n es cualquier número entero
sustituimos w:
$$x_{1} = 2 \pi n + \operatorname{asin}{\left(w_{1} \right)}$$
$$x_{1} = 2 \pi n + \operatorname{asin}{\left(- \frac{1}{2} \right)}$$
$$x_{1} = 2 \pi n - \frac{\pi}{6}$$
$$x_{2} = 2 \pi n + \operatorname{asin}{\left(w_{2} \right)}$$
$$x_{2} = 2 \pi n + \operatorname{asin}{\left(3 \right)}$$
$$x_{2} = 2 \pi n + \operatorname{asin}{\left(3 \right)}$$
$$x_{3} = 2 \pi n - \operatorname{asin}{\left(w_{1} \right)} + \pi$$
$$x_{3} = 2 \pi n - \operatorname{asin}{\left(- \frac{1}{2} \right)} + \pi$$
$$x_{3} = 2 \pi n + \frac{7 \pi}{6}$$
$$x_{4} = 2 \pi n - \operatorname{asin}{\left(w_{2} \right)} + \pi$$
$$x_{4} = 2 \pi n + \pi - \operatorname{asin}{\left(3 \right)}$$
$$x_{4} = 2 \pi n + \pi - \operatorname{asin}{\left(3 \right)}$$
$$x_{1} = 100.007366139275$$
$$x_{2} = -82.2050077689329$$
$$x_{3} = 68.5914396033772$$
$$x_{4} = 87.4409955249159$$
$$x_{5} = -45867.7763411866$$
$$x_{6} = -71.733032256967$$
$$x_{7} = 41.3643032722656$$
$$x_{8} = 74.8746249105567$$
$$x_{9} = 12.0427718387609$$
$$x_{10} = -65.4498469497874$$
$$x_{11} = 37.1755130674792$$
$$x_{12} = 110.479341651241$$
$$x_{13} = 22.5147473507269$$
$$x_{14} = 30.8923277602996$$
$$x_{15} = -15.1843644923507$$
$$x_{16} = 81.1578102177363$$
$$x_{17} = 62.3082542961976$$
$$x_{18} = -59.1666616426078$$
$$x_{19} = 93.7241808320955$$
$$x_{20} = 47.6474885794452$$
$$x_{21} = 56.025068989018$$
$$x_{22} = 91.6297857297023$$
$$x_{23} = 79.0634151153431$$
$$x_{24} = 18.3259571459405$$
$$x_{25} = 66.497044500984$$
$$x_{26} = -75.9218224617533$$
$$x_{27} = -239.284640448423$$
$$x_{28} = -31.9395253114962$$
$$x_{29} = -46.6002910282486$$
$$x_{30} = -101.054563690472$$
$$x_{31} = 28.7979326579064$$
$$x_{32} = 53.9306738866248$$
$$x_{33} = -90.5825881785057$$
$$x_{34} = -8.90117918517108$$
$$x_{35} = -6.80678408277789$$
$$x_{36} = -69.6386371545737$$
$$x_{37} = 60.2138591938044$$
$$x_{38} = -44.5058959258554$$
$$x_{39} = -94.7713783832921$$
$$x_{40} = -27.7507351067098$$
$$x_{41} = -25.6563400043166$$
$$x_{42} = -34.0339204138894$$
$$x_{43} = -50.789081233035$$
$$x_{44} = -13.0899693899575$$
$$x_{45} = 3.66519142918809$$
$$x_{46} = -88.4881930761125$$
$$x_{47} = 85.3466004225227$$
$$x_{48} = -84.2994028713261$$
$$x_{49} = 16.2315620435473$$
$$x_{50} = -52.8834763354282$$
$$x_{51} = -643.502895210309$$
$$x_{52} = -40.317105721069$$
$$x_{53} = -0.523598775598299$$
$$x_{54} = 97.9129710368819$$
$$x_{55} = 49.7418836818384$$
$$x_{56} = 35.081117965086$$
$$x_{57} = 791.15774992903$$
$$x_{58} = -96.8657734856853$$
$$x_{59} = 24.60914245312$$
$$x_{60} = 5.75958653158129$$
$$x_{61} = -21.4675497995303$$
$$x_{62} = -63.3554518473942$$
$$x_{63} = -78.0162175641465$$
$$x_{64} = -38.2227106186758$$
$$x_{65} = 72.7802298081635$$
$$x_{66} = 43.4586983746588$$
$$x_{67} = -2.61799387799149$$
$$x_{68} = 9.94837673636768$$
$$x_{69} = -57.0722665402146$$
$$x_{70} = 112.573736753634$$
$$x_{71} = -19.3731546971371$$
$$x_{1} = 100.007366139275$$
$$x_{2} = -82.2050077689329$$
$$x_{3} = 68.5914396033772$$
$$x_{4} = 87.4409955249159$$
$$x_{5} = -45867.7763411866$$
$$x_{6} = -71.733032256967$$
$$x_{7} = 41.3643032722656$$
$$x_{8} = 74.8746249105567$$
$$x_{9} = 12.0427718387609$$
$$x_{10} = -65.4498469497874$$
$$x_{11} = 37.1755130674792$$
$$x_{12} = 110.479341651241$$
$$x_{13} = 22.5147473507269$$
$$x_{14} = 30.8923277602996$$
$$x_{15} = -15.1843644923507$$
$$x_{16} = 81.1578102177363$$
$$x_{17} = 62.3082542961976$$
$$x_{18} = -59.1666616426078$$
$$x_{19} = 93.7241808320955$$
$$x_{20} = 47.6474885794452$$
$$x_{21} = 56.025068989018$$
$$x_{22} = 91.6297857297023$$
$$x_{23} = 79.0634151153431$$
$$x_{24} = 18.3259571459405$$
$$x_{25} = 66.497044500984$$
$$x_{26} = -75.9218224617533$$
$$x_{27} = -239.284640448423$$
$$x_{28} = -31.9395253114962$$
$$x_{29} = -46.6002910282486$$
$$x_{30} = -101.054563690472$$
$$x_{31} = 28.7979326579064$$
$$x_{32} = 53.9306738866248$$
$$x_{33} = -90.5825881785057$$
$$x_{34} = -8.90117918517108$$
$$x_{35} = -6.80678408277789$$
$$x_{36} = -69.6386371545737$$
$$x_{37} = 60.2138591938044$$
$$x_{38} = -44.5058959258554$$
$$x_{39} = -94.7713783832921$$
$$x_{40} = -27.7507351067098$$
$$x_{41} = -25.6563400043166$$
$$x_{42} = -34.0339204138894$$
$$x_{43} = -50.789081233035$$
$$x_{44} = -13.0899693899575$$
$$x_{45} = 3.66519142918809$$
$$x_{46} = -88.4881930761125$$
$$x_{47} = 85.3466004225227$$
$$x_{48} = -84.2994028713261$$
$$x_{49} = 16.2315620435473$$
$$x_{50} = -52.8834763354282$$
$$x_{51} = -643.502895210309$$
$$x_{52} = -40.317105721069$$
$$x_{53} = -0.523598775598299$$
$$x_{54} = 97.9129710368819$$
$$x_{55} = 49.7418836818384$$
$$x_{56} = 35.081117965086$$
$$x_{57} = 791.15774992903$$
$$x_{58} = -96.8657734856853$$
$$x_{59} = 24.60914245312$$
$$x_{60} = 5.75958653158129$$
$$x_{61} = -21.4675497995303$$
$$x_{62} = -63.3554518473942$$
$$x_{63} = -78.0162175641465$$
$$x_{64} = -38.2227106186758$$
$$x_{65} = 72.7802298081635$$
$$x_{66} = 43.4586983746588$$
$$x_{67} = -2.61799387799149$$
$$x_{68} = 9.94837673636768$$
$$x_{69} = -57.0722665402146$$
$$x_{70} = 112.573736753634$$
$$x_{71} = -19.3731546971371$$
Las raíces dadas
$$x_{5} = -45867.7763411866$$
$$x_{51} = -643.502895210309$$
$$x_{27} = -239.284640448423$$
$$x_{30} = -101.054563690472$$
$$x_{58} = -96.8657734856853$$
$$x_{39} = -94.7713783832921$$
$$x_{33} = -90.5825881785057$$
$$x_{46} = -88.4881930761125$$
$$x_{48} = -84.2994028713261$$
$$x_{2} = -82.2050077689329$$
$$x_{63} = -78.0162175641465$$
$$x_{26} = -75.9218224617533$$
$$x_{6} = -71.733032256967$$
$$x_{36} = -69.6386371545737$$
$$x_{10} = -65.4498469497874$$
$$x_{62} = -63.3554518473942$$
$$x_{18} = -59.1666616426078$$
$$x_{69} = -57.0722665402146$$
$$x_{50} = -52.8834763354282$$
$$x_{43} = -50.789081233035$$
$$x_{29} = -46.6002910282486$$
$$x_{38} = -44.5058959258554$$
$$x_{52} = -40.317105721069$$
$$x_{64} = -38.2227106186758$$
$$x_{42} = -34.0339204138894$$
$$x_{28} = -31.9395253114962$$
$$x_{40} = -27.7507351067098$$
$$x_{41} = -25.6563400043166$$
$$x_{61} = -21.4675497995303$$
$$x_{71} = -19.3731546971371$$
$$x_{15} = -15.1843644923507$$
$$x_{44} = -13.0899693899575$$
$$x_{34} = -8.90117918517108$$
$$x_{35} = -6.80678408277789$$
$$x_{67} = -2.61799387799149$$
$$x_{53} = -0.523598775598299$$
$$x_{45} = 3.66519142918809$$
$$x_{60} = 5.75958653158129$$
$$x_{68} = 9.94837673636768$$
$$x_{9} = 12.0427718387609$$
$$x_{49} = 16.2315620435473$$
$$x_{24} = 18.3259571459405$$
$$x_{13} = 22.5147473507269$$
$$x_{59} = 24.60914245312$$
$$x_{31} = 28.7979326579064$$
$$x_{14} = 30.8923277602996$$
$$x_{56} = 35.081117965086$$
$$x_{11} = 37.1755130674792$$
$$x_{7} = 41.3643032722656$$
$$x_{66} = 43.4586983746588$$
$$x_{20} = 47.6474885794452$$
$$x_{55} = 49.7418836818384$$
$$x_{32} = 53.9306738866248$$
$$x_{21} = 56.025068989018$$
$$x_{37} = 60.2138591938044$$
$$x_{17} = 62.3082542961976$$
$$x_{25} = 66.497044500984$$
$$x_{3} = 68.5914396033772$$
$$x_{65} = 72.7802298081635$$
$$x_{8} = 74.8746249105567$$
$$x_{23} = 79.0634151153431$$
$$x_{16} = 81.1578102177363$$
$$x_{47} = 85.3466004225227$$
$$x_{4} = 87.4409955249159$$
$$x_{22} = 91.6297857297023$$
$$x_{19} = 93.7241808320955$$
$$x_{54} = 97.9129710368819$$
$$x_{1} = 100.007366139275$$
$$x_{12} = 110.479341651241$$
$$x_{70} = 112.573736753634$$
$$x_{57} = 791.15774992903$$
son puntos de cambio del signo de desigualdad en las soluciones.
Primero definámonos con el signo hasta el punto extremo izquierdo:
$$x_{0} \leq x_{5}$$
Consideremos, por ejemplo, el punto
$$x_{0} = x_{5} - \frac{1}{10}$$
=
$$-45867.7763411866 + - \frac{1}{10}$$
=
$$-45867.8763411866$$
lo sustituimos en la expresión
$$5 \sin{\left(x \right)} + \cos{\left(2 x \right)} \geq -2$$
$$5 \sin{\left(-45867.8763411866 \right)} + \cos{\left(\left(-45867.8763411866\right) 2 \right)} \geq -2$$
-2.60182118651354 >= -2

pero
-2.60182118651354 < -2

Entonces
$$x \leq -45867.7763411866$$
no se cumple
significa que una de las soluciones de nuestra ecuación será con:
$$x \geq -45867.7763411866 \wedge x \leq -643.502895210309$$
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       x5      x51      x27      x30      x58      x39      x33      x46      x48      x2      x63      x26      x6      x36      x10      x62      x18      x69      x50      x43      x29      x38      x52      x64      x42      x28      x40      x41      x61      x71      x15      x44      x34      x35      x67      x53      x45      x60      x68      x9      x49      x24      x13      x59      x31      x14      x56      x11      x7      x66      x20      x55      x32      x21      x37      x17      x25      x3      x65      x8      x23      x16      x47      x4      x22      x19      x54      x1      x12      x70      x57

Recibiremos otras soluciones de la desigualdad pasando al polo siguiente etc.
etc.
Respuesta:
$$x \geq -45867.7763411866 \wedge x \leq -643.502895210309$$
$$x \geq -239.284640448423 \wedge x \leq -101.054563690472$$
$$x \geq -96.8657734856853 \wedge x \leq -94.7713783832921$$
$$x \geq -90.5825881785057 \wedge x \leq -88.4881930761125$$
$$x \geq -84.2994028713261 \wedge x \leq -82.2050077689329$$
$$x \geq -78.0162175641465 \wedge x \leq -75.9218224617533$$
$$x \geq -71.733032256967 \wedge x \leq -69.6386371545737$$
$$x \geq -65.4498469497874 \wedge x \leq -63.3554518473942$$
$$x \geq -59.1666616426078 \wedge x \leq -57.0722665402146$$
$$x \geq -52.8834763354282 \wedge x \leq -50.789081233035$$
$$x \geq -46.6002910282486 \wedge x \leq -44.5058959258554$$
$$x \geq -40.317105721069 \wedge x \leq -38.2227106186758$$
$$x \geq -34.0339204138894 \wedge x \leq -31.9395253114962$$
$$x \geq -27.7507351067098 \wedge x \leq -25.6563400043166$$
$$x \geq -21.4675497995303 \wedge x \leq -19.3731546971371$$
$$x \geq -15.1843644923507 \wedge x \leq -13.0899693899575$$
$$x \geq -8.90117918517108 \wedge x \leq -6.80678408277789$$
$$x \geq -2.61799387799149 \wedge x \leq -0.523598775598299$$
$$x \geq 3.66519142918809 \wedge x \leq 5.75958653158129$$
$$x \geq 9.94837673636768 \wedge x \leq 12.0427718387609$$
$$x \geq 16.2315620435473 \wedge x \leq 18.3259571459405$$
$$x \geq 22.5147473507269 \wedge x \leq 24.60914245312$$
$$x \geq 28.7979326579064 \wedge x \leq 30.8923277602996$$
$$x \geq 35.081117965086 \wedge x \leq 37.1755130674792$$
$$x \geq 41.3643032722656 \wedge x \leq 43.4586983746588$$
$$x \geq 47.6474885794452 \wedge x \leq 49.7418836818384$$
$$x \geq 53.9306738866248 \wedge x \leq 56.025068989018$$
$$x \geq 60.2138591938044 \wedge x \leq 62.3082542961976$$
$$x \geq 66.497044500984 \wedge x \leq 68.5914396033772$$
$$x \geq 72.7802298081635 \wedge x \leq 74.8746249105567$$
$$x \geq 79.0634151153431 \wedge x \leq 81.1578102177363$$
$$x \geq 85.3466004225227 \wedge x \leq 87.4409955249159$$
$$x \geq 91.6297857297023 \wedge x \leq 93.7241808320955$$
$$x \geq 97.9129710368819 \wedge x \leq 100.007366139275$$
$$x \geq 110.479341651241 \wedge x \leq 112.573736753634$$
$$x \geq 791.15774992903$$
Solución de la desigualdad en el gráfico
Respuesta rápida [src]
  /   /             7*pi\     /11*pi                \\
Or|And|0 <= x, x <= ----|, And|----- <= x, x <= 2*pi||
  \   \              6  /     \  6                  //
$$\left(0 \leq x \wedge x \leq \frac{7 \pi}{6}\right) \vee \left(\frac{11 \pi}{6} \leq x \wedge x \leq 2 \pi\right)$$
((0 <= x)∧(x <= 7*pi/6))∨((11*pi/6 <= x)∧(x <= 2*pi))
Respuesta rápida 2 [src]
    7*pi     11*pi       
[0, ----] U [-----, 2*pi]
     6         6         
$$x\ in\ \left[0, \frac{7 \pi}{6}\right] \cup \left[\frac{11 \pi}{6}, 2 \pi\right]$$
x in Union(Interval(0, 7*pi/6), Interval(11*pi/6, 2*pi))