Se da la desigualdad:
$$\left(x 3 \cos{\left(x \right)} + x 2 \cos^{2}{\left(x \right)}\right) - 2 < 0$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$\left(x 3 \cos{\left(x \right)} + x 2 \cos^{2}{\left(x \right)}\right) - 2 = 0$$
Resolvemos:
$$x_{1} = 73.8364027462792$$
$$x_{2} = 61.2718596272267$$
$$x_{3} = 64.3923665126583$$
$$x_{4} = -73.8183410155392$$
$$x_{5} = -54.9656426538452$$
$$x_{6} = -7.94333705294662$$
$$x_{7} = 4.83972949870642$$
$$x_{8} = -39.2870745597143$$
$$x_{9} = -92.6697543756021$$
$$x_{10} = -33.0072014491741$$
$$x_{11} = 1.08247762879257$$
$$x_{12} = 29.8671304442391$$
$$x_{13} = 32.9667646686781$$
$$x_{14} = 83.2442389811335$$
$$x_{15} = -20.4536931796381$$
$$x_{16} = 42.4270534518348$$
$$x_{17} = 51.8235227390457$$
$$x_{18} = 11.0536711207503$$
$$x_{19} = 7.77253236164003$$
$$x_{20} = -58.1310217435679$$
$$x_{21} = 80.118888074651$$
$$x_{22} = -86.3860404813383$$
$$x_{23} = 54.9898987339094$$
$$x_{24} = 58.1080774050884$$
$$x_{25} = -2.06189512827871$$
$$x_{26} = 92.6841420653101$$
$$x_{27} = -76.9777312253131$$
$$x_{28} = -17.2390251987658$$
$$x_{29} = -98.9534008238778$$
$$x_{30} = 14.0912449977744$$
$$x_{31} = 26.6789495533166$$
$$x_{32} = -10.931843121774$$
$$x_{33} = -36.1096191160295$$
$$x_{34} = -14.185754131777$$
$$x_{35} = -64.413071869325$$
$$x_{36} = 67.5540467645286$$
$$x_{37} = 39.2531116528389$$
$$x_{38} = 70.6764604956629$$
$$x_{39} = -61.250092041306$$
$$x_{40} = 89.5279807019346$$
$$x_{41} = -45.5678697547081$$
$$x_{42} = 23.5896961026034$$
$$x_{43} = -48.6808636902234$$
$$x_{44} = 36.1465386061925$$
$$x_{45} = 0.468499276211058$$
$$x_{46} = 86.4014746797018$$
$$x_{47} = -42.3956068566195$$
$$x_{48} = -89.5428732459059$$
$$x_{49} = -95.8255656472355$$
$$x_{50} = 17.3163272961097$$
$$x_{51} = 76.9604068995183$$
$$x_{52} = 20.388331647698$$
$$x_{53} = -26.728911181592$$
$$x_{54} = 45.5385935276166$$
$$x_{55} = -70.6953250285163$$
$$x_{56} = 98.9668749162376$$
$$x_{57} = -80.1022431743895$$
$$x_{58} = -51.8492490822935$$
$$x_{59} = -83.2602556327887$$
$$x_{60} = 48.708250821989$$
$$x_{61} = 95.811649763727$$
$$x_{62} = -23.5330557017427$$
$$x_{63} = -4.54693110505134$$
$$x_{64} = -67.5343045281809$$
$$x_{65} = -29.8224302548231$$
$$x_{1} = 73.8364027462792$$
$$x_{2} = 61.2718596272267$$
$$x_{3} = 64.3923665126583$$
$$x_{4} = -73.8183410155392$$
$$x_{5} = -54.9656426538452$$
$$x_{6} = -7.94333705294662$$
$$x_{7} = 4.83972949870642$$
$$x_{8} = -39.2870745597143$$
$$x_{9} = -92.6697543756021$$
$$x_{10} = -33.0072014491741$$
$$x_{11} = 1.08247762879257$$
$$x_{12} = 29.8671304442391$$
$$x_{13} = 32.9667646686781$$
$$x_{14} = 83.2442389811335$$
$$x_{15} = -20.4536931796381$$
$$x_{16} = 42.4270534518348$$
$$x_{17} = 51.8235227390457$$
$$x_{18} = 11.0536711207503$$
$$x_{19} = 7.77253236164003$$
$$x_{20} = -58.1310217435679$$
$$x_{21} = 80.118888074651$$
$$x_{22} = -86.3860404813383$$
$$x_{23} = 54.9898987339094$$
$$x_{24} = 58.1080774050884$$
$$x_{25} = -2.06189512827871$$
$$x_{26} = 92.6841420653101$$
$$x_{27} = -76.9777312253131$$
$$x_{28} = -17.2390251987658$$
$$x_{29} = -98.9534008238778$$
$$x_{30} = 14.0912449977744$$
$$x_{31} = 26.6789495533166$$
$$x_{32} = -10.931843121774$$
$$x_{33} = -36.1096191160295$$
$$x_{34} = -14.185754131777$$
$$x_{35} = -64.413071869325$$
$$x_{36} = 67.5540467645286$$
$$x_{37} = 39.2531116528389$$
$$x_{38} = 70.6764604956629$$
$$x_{39} = -61.250092041306$$
$$x_{40} = 89.5279807019346$$
$$x_{41} = -45.5678697547081$$
$$x_{42} = 23.5896961026034$$
$$x_{43} = -48.6808636902234$$
$$x_{44} = 36.1465386061925$$
$$x_{45} = 0.468499276211058$$
$$x_{46} = 86.4014746797018$$
$$x_{47} = -42.3956068566195$$
$$x_{48} = -89.5428732459059$$
$$x_{49} = -95.8255656472355$$
$$x_{50} = 17.3163272961097$$
$$x_{51} = 76.9604068995183$$
$$x_{52} = 20.388331647698$$
$$x_{53} = -26.728911181592$$
$$x_{54} = 45.5385935276166$$
$$x_{55} = -70.6953250285163$$
$$x_{56} = 98.9668749162376$$
$$x_{57} = -80.1022431743895$$
$$x_{58} = -51.8492490822935$$
$$x_{59} = -83.2602556327887$$
$$x_{60} = 48.708250821989$$
$$x_{61} = 95.811649763727$$
$$x_{62} = -23.5330557017427$$
$$x_{63} = -4.54693110505134$$
$$x_{64} = -67.5343045281809$$
$$x_{65} = -29.8224302548231$$
Las raíces dadas
$$x_{29} = -98.9534008238778$$
$$x_{49} = -95.8255656472355$$
$$x_{9} = -92.6697543756021$$
$$x_{48} = -89.5428732459059$$
$$x_{22} = -86.3860404813383$$
$$x_{59} = -83.2602556327887$$
$$x_{57} = -80.1022431743895$$
$$x_{27} = -76.9777312253131$$
$$x_{4} = -73.8183410155392$$
$$x_{55} = -70.6953250285163$$
$$x_{64} = -67.5343045281809$$
$$x_{35} = -64.413071869325$$
$$x_{39} = -61.250092041306$$
$$x_{20} = -58.1310217435679$$
$$x_{5} = -54.9656426538452$$
$$x_{58} = -51.8492490822935$$
$$x_{43} = -48.6808636902234$$
$$x_{41} = -45.5678697547081$$
$$x_{47} = -42.3956068566195$$
$$x_{8} = -39.2870745597143$$
$$x_{33} = -36.1096191160295$$
$$x_{10} = -33.0072014491741$$
$$x_{65} = -29.8224302548231$$
$$x_{53} = -26.728911181592$$
$$x_{62} = -23.5330557017427$$
$$x_{15} = -20.4536931796381$$
$$x_{28} = -17.2390251987658$$
$$x_{34} = -14.185754131777$$
$$x_{32} = -10.931843121774$$
$$x_{6} = -7.94333705294662$$
$$x_{63} = -4.54693110505134$$
$$x_{25} = -2.06189512827871$$
$$x_{45} = 0.468499276211058$$
$$x_{11} = 1.08247762879257$$
$$x_{7} = 4.83972949870642$$
$$x_{19} = 7.77253236164003$$
$$x_{18} = 11.0536711207503$$
$$x_{30} = 14.0912449977744$$
$$x_{50} = 17.3163272961097$$
$$x_{52} = 20.388331647698$$
$$x_{42} = 23.5896961026034$$
$$x_{31} = 26.6789495533166$$
$$x_{12} = 29.8671304442391$$
$$x_{13} = 32.9667646686781$$
$$x_{44} = 36.1465386061925$$
$$x_{37} = 39.2531116528389$$
$$x_{16} = 42.4270534518348$$
$$x_{54} = 45.5385935276166$$
$$x_{60} = 48.708250821989$$
$$x_{17} = 51.8235227390457$$
$$x_{23} = 54.9898987339094$$
$$x_{24} = 58.1080774050884$$
$$x_{2} = 61.2718596272267$$
$$x_{3} = 64.3923665126583$$
$$x_{36} = 67.5540467645286$$
$$x_{38} = 70.6764604956629$$
$$x_{1} = 73.8364027462792$$
$$x_{51} = 76.9604068995183$$
$$x_{21} = 80.118888074651$$
$$x_{14} = 83.2442389811335$$
$$x_{46} = 86.4014746797018$$
$$x_{40} = 89.5279807019346$$
$$x_{26} = 92.6841420653101$$
$$x_{61} = 95.811649763727$$
$$x_{56} = 98.9668749162376$$
son puntos de cambio del signo de desigualdad en las soluciones.
Primero definámonos con el signo hasta el punto extremo izquierdo:
$$x_{0} < x_{29}$$
Consideremos, por ejemplo, el punto
$$x_{0} = x_{29} - \frac{1}{10}$$
=
$$-98.9534008238778 + - \frac{1}{10}$$
=
$$-99.0534008238778$$
lo sustituimos en la expresión
$$\left(x 3 \cos{\left(x \right)} + x 2 \cos^{2}{\left(x \right)}\right) - 2 < 0$$
$$\left(\left(-99.0534008238778\right) 3 \cos{\left(-99.0534008238778 \right)} + \left(-99.0534008238778\right) 2 \cos^{2}{\left(-99.0534008238778 \right)}\right) - 2 < 0$$
-31.3818014249216 < 0
significa que una de las soluciones de nuestra ecuación será con:
$$x < -98.9534008238778$$
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\ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \
-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------ο-------
x29 x49 x9 x48 x22 x59 x57 x27 x4 x55 x64 x35 x39 x20 x5 x58 x43 x41 x47 x8 x33 x10 x65 x53 x62 x15 x28 x34 x32 x6 x63 x25 x45 x11 x7 x19 x18 x30 x50 x52 x42 x31 x12 x13 x44 x37 x16 x54 x60 x17 x23 x24 x2 x3 x36 x38 x1 x51 x21 x14 x46 x40 x26 x61 x56
Recibiremos otras soluciones de la desigualdad pasando al polo siguiente etc.
etc.
Respuesta:
$$x < -98.9534008238778$$
$$x > -95.8255656472355 \wedge x < -92.6697543756021$$
$$x > -89.5428732459059 \wedge x < -86.3860404813383$$
$$x > -83.2602556327887 \wedge x < -80.1022431743895$$
$$x > -76.9777312253131 \wedge x < -73.8183410155392$$
$$x > -70.6953250285163 \wedge x < -67.5343045281809$$
$$x > -64.413071869325 \wedge x < -61.250092041306$$
$$x > -58.1310217435679 \wedge x < -54.9656426538452$$
$$x > -51.8492490822935 \wedge x < -48.6808636902234$$
$$x > -45.5678697547081 \wedge x < -42.3956068566195$$
$$x > -39.2870745597143 \wedge x < -36.1096191160295$$
$$x > -33.0072014491741 \wedge x < -29.8224302548231$$
$$x > -26.728911181592 \wedge x < -23.5330557017427$$
$$x > -20.4536931796381 \wedge x < -17.2390251987658$$
$$x > -14.185754131777 \wedge x < -10.931843121774$$
$$x > -7.94333705294662 \wedge x < -4.54693110505134$$
$$x > -2.06189512827871 \wedge x < 0.468499276211058$$
$$x > 1.08247762879257 \wedge x < 4.83972949870642$$
$$x > 7.77253236164003 \wedge x < 11.0536711207503$$
$$x > 14.0912449977744 \wedge x < 17.3163272961097$$
$$x > 20.388331647698 \wedge x < 23.5896961026034$$
$$x > 26.6789495533166 \wedge x < 29.8671304442391$$
$$x > 32.9667646686781 \wedge x < 36.1465386061925$$
$$x > 39.2531116528389 \wedge x < 42.4270534518348$$
$$x > 45.5385935276166 \wedge x < 48.708250821989$$
$$x > 51.8235227390457 \wedge x < 54.9898987339094$$
$$x > 58.1080774050884 \wedge x < 61.2718596272267$$
$$x > 64.3923665126583 \wedge x < 67.5540467645286$$
$$x > 70.6764604956629 \wedge x < 73.8364027462792$$
$$x > 76.9604068995183 \wedge x < 80.118888074651$$
$$x > 83.2442389811335 \wedge x < 86.4014746797018$$
$$x > 89.5279807019346 \wedge x < 92.6841420653101$$
$$x > 95.811649763727 \wedge x < 98.9668749162376$$