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sinxcos2x+cosxsin2x>1/2 desigualdades

En la desigualdad la incógnita

Solución

Ha introducido [src]
sin(x)*cos(2*x) + cos(x)*sin(2*x) > 1/2
$$\sin{\left(x \right)} \cos{\left(2 x \right)} + \sin{\left(2 x \right)} \cos{\left(x \right)} > \frac{1}{2}$$
sin(x)*cos(2*x) + sin(2*x)*cos(x) > 1/2
Solución detallada
Se da la desigualdad:
$$\sin{\left(x \right)} \cos{\left(2 x \right)} + \sin{\left(2 x \right)} \cos{\left(x \right)} > \frac{1}{2}$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$\sin{\left(x \right)} \cos{\left(2 x \right)} + \sin{\left(2 x \right)} \cos{\left(x \right)} = \frac{1}{2}$$
Resolvemos:
$$x_{1} = 6.45771823237902$$
$$x_{2} = 78.3652834145454$$
$$x_{3} = -13.7881010907552$$
$$x_{4} = 83.9503370209273$$
$$x_{5} = -85.6956662729216$$
$$x_{6} = 65.7989128001862$$
$$x_{7} = -45.9021593274509$$
$$x_{8} = 76.2708883121522$$
$$x_{9} = -77.3180858633488$$
$$x_{10} = 50.4400153826361$$
$$x_{11} = 19.7222205475359$$
$$x_{12} = -22.8638132011257$$
$$x_{13} = -43.8077642250577$$
$$x_{14} = -20.0712863979348$$
$$x_{15} = -83.6012711705284$$
$$x_{16} = 63.704517697793$$
$$x_{17} = -68.2423737529783$$
$$x_{18} = 28.0998009571087$$
$$x_{19} = 34.3829862642883$$
$$x_{20} = 39.9680398706701$$
$$x_{21} = -61.9591884457987$$
$$x_{22} = 30.1941960595019$$
$$x_{23} = -11.693705988362$$
$$x_{24} = -87.7900613753148$$
$$x_{25} = 44.1568300754565$$
$$x_{26} = -97.563905186483$$
$$x_{27} = 74.176493209759$$
$$x_{28} = 4.36332312998582$$
$$x_{29} = -15.8824961931484$$
$$x_{30} = 61.6101225953998$$
$$x_{31} = 86.0447321233204$$
$$x_{32} = -41.7133691226645$$
$$x_{33} = 42.0624349730633$$
$$x_{34} = -4.01425727958696$$
$$x_{35} = 46.2512251778497$$
$$x_{36} = 96.5167076352864$$
$$x_{37} = -81.5068760681352$$
$$x_{38} = 54.6288055874225$$
$$x_{39} = -47.9965544298441$$
$$x_{40} = -24.9582083035189$$
$$x_{41} = 21.8166156499291$$
$$x_{42} = -6.10865238198015$$
$$x_{43} = -37.5245789178781$$
$$x_{44} = -91.9788515801012$$
$$x_{45} = -53.5816080362259$$
$$x_{46} = -73.1292956585624$$
$$x_{47} = -1.22173047639603$$
$$x_{48} = 60.9119908946021$$
$$x_{49} = 37.873644768277$$
$$x_{50} = -9.59931088596881$$
$$x_{51} = -79.412480965742$$
$$x_{52} = -64.0535835481919$$
$$x_{53} = 8.55211333477222$$
$$x_{54} = 10.6465084371654$$
$$x_{55} = -1.91986217719376$$
$$x_{56} = 26.0054058547155$$
$$x_{57} = -34.7320521146872$$
$$x_{58} = -52.1853446346305$$
$$x_{59} = -59.8647933434055$$
$$x_{60} = -94.0732466824944$$
$$x_{61} = -26.3544717051144$$
$$x_{62} = -99.6583002888762$$
$$x_{63} = -70.3367688553715$$
$$x_{64} = 0.174532925199433$$
$$x_{65} = 88.1391272257137$$
$$x_{66} = -50.0909495322373$$
$$x_{67} = -29.1469985083053$$
$$x_{68} = -72.4311639577647$$
$$x_{69} = 72.0820981073658$$
$$x_{70} = 98.6111027376796$$
$$x_{71} = 52.5344104850293$$
$$x_{72} = -55.6760031386191$$
$$x_{73} = -39.6189740202713$$
$$x_{74} = 92.3279174305$$
$$x_{75} = -96.1676417848876$$
$$x_{76} = 103.498024643264$$
$$x_{77} = 94.4223125328932$$
$$x_{78} = -17.9768912955416$$
$$x_{79} = 13.4390352403563$$
$$x_{80} = -89.884456477708$$
$$x_{81} = -66.1479786505851$$
$$x_{82} = 67.8933079025794$$
$$x_{83} = -22.165681500328$$
$$x_{84} = 69.9877030049726$$
$$x_{85} = 2.26892802759263$$
$$x_{86} = 23.9110107523223$$
$$x_{87} = 90.2335223281068$$
$$x_{88} = 32.2885911618951$$
$$x_{89} = -76.6199541625511$$
$$x_{90} = -24.2600766027212$$
$$x_{91} = 101.403629540871$$
$$x_{92} = -57.7703982410123$$
$$x_{93} = -35.4301838154849$$
$$x_{94} = 81.8559419185341$$
$$x_{95} = 17.6278254451427$$
$$x_{96} = 48.3456202802429$$
$$x_{1} = 6.45771823237902$$
$$x_{2} = 78.3652834145454$$
$$x_{3} = -13.7881010907552$$
$$x_{4} = 83.9503370209273$$
$$x_{5} = -85.6956662729216$$
$$x_{6} = 65.7989128001862$$
$$x_{7} = -45.9021593274509$$
$$x_{8} = 76.2708883121522$$
$$x_{9} = -77.3180858633488$$
$$x_{10} = 50.4400153826361$$
$$x_{11} = 19.7222205475359$$
$$x_{12} = -22.8638132011257$$
$$x_{13} = -43.8077642250577$$
$$x_{14} = -20.0712863979348$$
$$x_{15} = -83.6012711705284$$
$$x_{16} = 63.704517697793$$
$$x_{17} = -68.2423737529783$$
$$x_{18} = 28.0998009571087$$
$$x_{19} = 34.3829862642883$$
$$x_{20} = 39.9680398706701$$
$$x_{21} = -61.9591884457987$$
$$x_{22} = 30.1941960595019$$
$$x_{23} = -11.693705988362$$
$$x_{24} = -87.7900613753148$$
$$x_{25} = 44.1568300754565$$
$$x_{26} = -97.563905186483$$
$$x_{27} = 74.176493209759$$
$$x_{28} = 4.36332312998582$$
$$x_{29} = -15.8824961931484$$
$$x_{30} = 61.6101225953998$$
$$x_{31} = 86.0447321233204$$
$$x_{32} = -41.7133691226645$$
$$x_{33} = 42.0624349730633$$
$$x_{34} = -4.01425727958696$$
$$x_{35} = 46.2512251778497$$
$$x_{36} = 96.5167076352864$$
$$x_{37} = -81.5068760681352$$
$$x_{38} = 54.6288055874225$$
$$x_{39} = -47.9965544298441$$
$$x_{40} = -24.9582083035189$$
$$x_{41} = 21.8166156499291$$
$$x_{42} = -6.10865238198015$$
$$x_{43} = -37.5245789178781$$
$$x_{44} = -91.9788515801012$$
$$x_{45} = -53.5816080362259$$
$$x_{46} = -73.1292956585624$$
$$x_{47} = -1.22173047639603$$
$$x_{48} = 60.9119908946021$$
$$x_{49} = 37.873644768277$$
$$x_{50} = -9.59931088596881$$
$$x_{51} = -79.412480965742$$
$$x_{52} = -64.0535835481919$$
$$x_{53} = 8.55211333477222$$
$$x_{54} = 10.6465084371654$$
$$x_{55} = -1.91986217719376$$
$$x_{56} = 26.0054058547155$$
$$x_{57} = -34.7320521146872$$
$$x_{58} = -52.1853446346305$$
$$x_{59} = -59.8647933434055$$
$$x_{60} = -94.0732466824944$$
$$x_{61} = -26.3544717051144$$
$$x_{62} = -99.6583002888762$$
$$x_{63} = -70.3367688553715$$
$$x_{64} = 0.174532925199433$$
$$x_{65} = 88.1391272257137$$
$$x_{66} = -50.0909495322373$$
$$x_{67} = -29.1469985083053$$
$$x_{68} = -72.4311639577647$$
$$x_{69} = 72.0820981073658$$
$$x_{70} = 98.6111027376796$$
$$x_{71} = 52.5344104850293$$
$$x_{72} = -55.6760031386191$$
$$x_{73} = -39.6189740202713$$
$$x_{74} = 92.3279174305$$
$$x_{75} = -96.1676417848876$$
$$x_{76} = 103.498024643264$$
$$x_{77} = 94.4223125328932$$
$$x_{78} = -17.9768912955416$$
$$x_{79} = 13.4390352403563$$
$$x_{80} = -89.884456477708$$
$$x_{81} = -66.1479786505851$$
$$x_{82} = 67.8933079025794$$
$$x_{83} = -22.165681500328$$
$$x_{84} = 69.9877030049726$$
$$x_{85} = 2.26892802759263$$
$$x_{86} = 23.9110107523223$$
$$x_{87} = 90.2335223281068$$
$$x_{88} = 32.2885911618951$$
$$x_{89} = -76.6199541625511$$
$$x_{90} = -24.2600766027212$$
$$x_{91} = 101.403629540871$$
$$x_{92} = -57.7703982410123$$
$$x_{93} = -35.4301838154849$$
$$x_{94} = 81.8559419185341$$
$$x_{95} = 17.6278254451427$$
$$x_{96} = 48.3456202802429$$
Las raíces dadas
$$x_{62} = -99.6583002888762$$
$$x_{26} = -97.563905186483$$
$$x_{75} = -96.1676417848876$$
$$x_{60} = -94.0732466824944$$
$$x_{44} = -91.9788515801012$$
$$x_{80} = -89.884456477708$$
$$x_{24} = -87.7900613753148$$
$$x_{5} = -85.6956662729216$$
$$x_{15} = -83.6012711705284$$
$$x_{37} = -81.5068760681352$$
$$x_{51} = -79.412480965742$$
$$x_{9} = -77.3180858633488$$
$$x_{89} = -76.6199541625511$$
$$x_{46} = -73.1292956585624$$
$$x_{68} = -72.4311639577647$$
$$x_{63} = -70.3367688553715$$
$$x_{17} = -68.2423737529783$$
$$x_{81} = -66.1479786505851$$
$$x_{52} = -64.0535835481919$$
$$x_{21} = -61.9591884457987$$
$$x_{59} = -59.8647933434055$$
$$x_{92} = -57.7703982410123$$
$$x_{72} = -55.6760031386191$$
$$x_{45} = -53.5816080362259$$
$$x_{58} = -52.1853446346305$$
$$x_{66} = -50.0909495322373$$
$$x_{39} = -47.9965544298441$$
$$x_{7} = -45.9021593274509$$
$$x_{13} = -43.8077642250577$$
$$x_{32} = -41.7133691226645$$
$$x_{73} = -39.6189740202713$$
$$x_{43} = -37.5245789178781$$
$$x_{93} = -35.4301838154849$$
$$x_{57} = -34.7320521146872$$
$$x_{67} = -29.1469985083053$$
$$x_{61} = -26.3544717051144$$
$$x_{40} = -24.9582083035189$$
$$x_{90} = -24.2600766027212$$
$$x_{12} = -22.8638132011257$$
$$x_{83} = -22.165681500328$$
$$x_{14} = -20.0712863979348$$
$$x_{78} = -17.9768912955416$$
$$x_{29} = -15.8824961931484$$
$$x_{3} = -13.7881010907552$$
$$x_{23} = -11.693705988362$$
$$x_{50} = -9.59931088596881$$
$$x_{42} = -6.10865238198015$$
$$x_{34} = -4.01425727958696$$
$$x_{55} = -1.91986217719376$$
$$x_{47} = -1.22173047639603$$
$$x_{64} = 0.174532925199433$$
$$x_{85} = 2.26892802759263$$
$$x_{28} = 4.36332312998582$$
$$x_{1} = 6.45771823237902$$
$$x_{53} = 8.55211333477222$$
$$x_{54} = 10.6465084371654$$
$$x_{79} = 13.4390352403563$$
$$x_{95} = 17.6278254451427$$
$$x_{11} = 19.7222205475359$$
$$x_{41} = 21.8166156499291$$
$$x_{86} = 23.9110107523223$$
$$x_{56} = 26.0054058547155$$
$$x_{18} = 28.0998009571087$$
$$x_{22} = 30.1941960595019$$
$$x_{88} = 32.2885911618951$$
$$x_{19} = 34.3829862642883$$
$$x_{49} = 37.873644768277$$
$$x_{20} = 39.9680398706701$$
$$x_{33} = 42.0624349730633$$
$$x_{25} = 44.1568300754565$$
$$x_{35} = 46.2512251778497$$
$$x_{96} = 48.3456202802429$$
$$x_{10} = 50.4400153826361$$
$$x_{71} = 52.5344104850293$$
$$x_{38} = 54.6288055874225$$
$$x_{48} = 60.9119908946021$$
$$x_{30} = 61.6101225953998$$
$$x_{16} = 63.704517697793$$
$$x_{6} = 65.7989128001862$$
$$x_{82} = 67.8933079025794$$
$$x_{84} = 69.9877030049726$$
$$x_{69} = 72.0820981073658$$
$$x_{27} = 74.176493209759$$
$$x_{8} = 76.2708883121522$$
$$x_{2} = 78.3652834145454$$
$$x_{94} = 81.8559419185341$$
$$x_{4} = 83.9503370209273$$
$$x_{31} = 86.0447321233204$$
$$x_{65} = 88.1391272257137$$
$$x_{87} = 90.2335223281068$$
$$x_{74} = 92.3279174305$$
$$x_{77} = 94.4223125328932$$
$$x_{36} = 96.5167076352864$$
$$x_{70} = 98.6111027376796$$
$$x_{91} = 101.403629540871$$
$$x_{76} = 103.498024643264$$
son puntos de cambio del signo de desigualdad en las soluciones.
Primero definámonos con el signo hasta el punto extremo izquierdo:
$$x_{0} < x_{62}$$
Consideremos, por ejemplo, el punto
$$x_{0} = x_{62} - \frac{1}{10}$$
=
$$-99.6583002888762 + - \frac{1}{10}$$
=
$$-99.7583002888762$$
lo sustituimos en la expresión
$$\sin{\left(x \right)} \cos{\left(2 x \right)} + \sin{\left(2 x \right)} \cos{\left(x \right)} > \frac{1}{2}$$
$$\sin{\left(-99.7583002888762 \right)} \cos{\left(\left(-99.7583002888762\right) 2 \right)} + \sin{\left(\left(-99.7583002888762\right) 2 \right)} \cos{\left(-99.7583002888762 \right)} > \frac{1}{2}$$
0.733596250863140 > 1/2

significa que una de las soluciones de nuestra ecuación será con:
$$x < -99.6583002888762$$
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       x62      x26      x75      x60      x44      x80      x24      x5      x15      x37      x51      x9      x89      x46      x68      x63      x17      x81      x52      x21      x59      x92      x72      x45      x58      x66      x39      x7      x13      x32      x73      x43      x93      x57      x67      x61      x40      x90      x12      x83      x14      x78      x29      x3      x23      x50      x42      x34      x55      x47      x64      x85      x28      x1      x53      x54      x79      x95      x11      x41      x86      x56      x18      x22      x88      x19      x49      x20      x33      x25      x35      x96      x10      x71      x38      x48      x30      x16      x6      x82      x84      x69      x27      x8      x2      x94      x4      x31      x65      x87      x74      x77      x36      x70      x91      x76

Recibiremos otras soluciones de la desigualdad pasando al polo siguiente etc.
etc.
Respuesta:
$$x < -99.6583002888762$$
$$x > -97.563905186483 \wedge x < -96.1676417848876$$
$$x > -94.0732466824944 \wedge x < -91.9788515801012$$
$$x > -89.884456477708 \wedge x < -87.7900613753148$$
$$x > -85.6956662729216 \wedge x < -83.6012711705284$$
$$x > -81.5068760681352 \wedge x < -79.412480965742$$
$$x > -77.3180858633488 \wedge x < -76.6199541625511$$
$$x > -73.1292956585624 \wedge x < -72.4311639577647$$
$$x > -70.3367688553715 \wedge x < -68.2423737529783$$
$$x > -66.1479786505851 \wedge x < -64.0535835481919$$
$$x > -61.9591884457987 \wedge x < -59.8647933434055$$
$$x > -57.7703982410123 \wedge x < -55.6760031386191$$
$$x > -53.5816080362259 \wedge x < -52.1853446346305$$
$$x > -50.0909495322373 \wedge x < -47.9965544298441$$
$$x > -45.9021593274509 \wedge x < -43.8077642250577$$
$$x > -41.7133691226645 \wedge x < -39.6189740202713$$
$$x > -37.5245789178781 \wedge x < -35.4301838154849$$
$$x > -34.7320521146872 \wedge x < -29.1469985083053$$
$$x > -26.3544717051144 \wedge x < -24.9582083035189$$
$$x > -24.2600766027212 \wedge x < -22.8638132011257$$
$$x > -22.165681500328 \wedge x < -20.0712863979348$$
$$x > -17.9768912955416 \wedge x < -15.8824961931484$$
$$x > -13.7881010907552 \wedge x < -11.693705988362$$
$$x > -9.59931088596881 \wedge x < -6.10865238198015$$
$$x > -4.01425727958696 \wedge x < -1.91986217719376$$
$$x > -1.22173047639603 \wedge x < 0.174532925199433$$
$$x > 2.26892802759263 \wedge x < 4.36332312998582$$
$$x > 6.45771823237902 \wedge x < 8.55211333477222$$
$$x > 10.6465084371654 \wedge x < 13.4390352403563$$
$$x > 17.6278254451427 \wedge x < 19.7222205475359$$
$$x > 21.8166156499291 \wedge x < 23.9110107523223$$
$$x > 26.0054058547155 \wedge x < 28.0998009571087$$
$$x > 30.1941960595019 \wedge x < 32.2885911618951$$
$$x > 34.3829862642883 \wedge x < 37.873644768277$$
$$x > 39.9680398706701 \wedge x < 42.0624349730633$$
$$x > 44.1568300754565 \wedge x < 46.2512251778497$$
$$x > 48.3456202802429 \wedge x < 50.4400153826361$$
$$x > 52.5344104850293 \wedge x < 54.6288055874225$$
$$x > 60.9119908946021 \wedge x < 61.6101225953998$$
$$x > 63.704517697793 \wedge x < 65.7989128001862$$
$$x > 67.8933079025794 \wedge x < 69.9877030049726$$
$$x > 72.0820981073658 \wedge x < 74.176493209759$$
$$x > 76.2708883121522 \wedge x < 78.3652834145454$$
$$x > 81.8559419185341 \wedge x < 83.9503370209273$$
$$x > 86.0447321233204 \wedge x < 88.1391272257137$$
$$x > 90.2335223281068 \wedge x < 92.3279174305$$
$$x > 94.4223125328932 \wedge x < 96.5167076352864$$
$$x > 98.6111027376796 \wedge x < 101.403629540871$$
$$x > 103.498024643264$$
Solución de la desigualdad en el gráfico
Respuesta rápida [src]
   /pi          5*pi\
And|-- < x, x < ----|
   \18           18 /
$$\frac{\pi}{18} < x \wedge x < \frac{5 \pi}{18}$$
(pi/18 < x)∧(x < 5*pi/18)
Respuesta rápida 2 [src]
 pi  5*pi 
(--, ----)
 18   18  
$$x\ in\ \left(\frac{\pi}{18}, \frac{5 \pi}{18}\right)$$
x in Interval.open(pi/18, 5*pi/18)