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sin2x<=-cbrt2/2 desigualdades

En la desigualdad la incógnita

Solución

Ha introducido [src]
             3 ___ 
            -\/ 2  
sin(2*x) <= -------
               2   
$$\sin{\left(2 x \right)} \leq \frac{\left(-1\right) \sqrt[3]{2}}{2}$$
sin(2*x) <= (-2^(1/3))/2
Solución detallada
Se da la desigualdad:
$$\sin{\left(2 x \right)} \leq \frac{\left(-1\right) \sqrt[3]{2}}{2}$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$\sin{\left(2 x \right)} = \frac{\left(-1\right) \sqrt[3]{2}}{2}$$
Resolvemos:
Tenemos la ecuación
$$\sin{\left(2 x \right)} = \frac{\left(-1\right) \sqrt[3]{2}}{2}$$
es la ecuación trigonométrica más simple
Esta ecuación se reorganiza en
$$2 x = 2 \pi n + \operatorname{asin}{\left(- \frac{\sqrt[3]{2}}{2} \right)}$$
$$2 x = 2 \pi n - \operatorname{asin}{\left(- \frac{\sqrt[3]{2}}{2} \right)} + \pi$$
O
$$2 x = 2 \pi n - \operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}$$
$$2 x = 2 \pi n + \operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)} + \pi$$
, donde n es cualquier número entero
Dividamos ambos miembros de la ecuación obtenida en
$$2$$
$$x_{1} = \pi n - \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2}$$
$$x_{2} = \pi n + \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2} + \frac{\pi}{2}$$
$$x_{1} = \pi n - \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2}$$
$$x_{2} = \pi n + \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2} + \frac{\pi}{2}$$
Las raíces dadas
$$x_{1} = \pi n - \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2}$$
$$x_{2} = \pi n + \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2} + \frac{\pi}{2}$$
son puntos de cambio del signo de desigualdad en las soluciones.
Primero definámonos con el signo hasta el punto extremo izquierdo:
$$x_{0} \leq x_{1}$$
Consideremos, por ejemplo, el punto
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$\left(\pi n - \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2}\right) + - \frac{1}{10}$$
=
$$\pi n - \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2} - \frac{1}{10}$$
lo sustituimos en la expresión
$$\sin{\left(2 x \right)} \leq \frac{\left(-1\right) \sqrt[3]{2}}{2}$$
$$\sin{\left(2 \left(\pi n - \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2} - \frac{1}{10}\right) \right)} \leq \frac{\left(-1\right) \sqrt[3]{2}}{2}$$
    /                 /3 ___\\     3 ___ 
    |1                |\/ 2 ||    -\/ 2  
-sin|- - 2*pi*n + asin|-----|| <= -------
    \5                \  2  //       2   
    

significa que una de las soluciones de nuestra ecuación será con:
$$x \leq \pi n - \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2}$$
 _____           _____          
      \         /
-------•-------•-------
       x1      x2

Recibiremos otras soluciones de la desigualdad pasando al polo siguiente etc.
etc.
Respuesta:
$$x \leq \pi n - \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2}$$
$$x \geq \pi n + \frac{\operatorname{asin}{\left(\frac{\sqrt[3]{2}}{2} \right)}}{2} + \frac{\pi}{2}$$
Solución de la desigualdad en el gráfico
Respuesta rápida [src]
   /        /  /         /   /    /    3 ___    \\\\                                                                        \     /  /         /   /    /    3 ___    \\\\                                                                        \     \
   |        |  |         |   |    |    \/ 2     ||||      /         _______________________________________________________\|     |  |         |   |    |    \/ 2     ||||      /         _______________________________________________________\|     |
   |        |  |         |   |atan|-------------||||      |        /     /    /    3 ___    \\       /    /    3 ___    \\ ||     |  |         |   |atan|-------------||||      |        /     /    /    3 ___    \\       /    /    3 ___    \\ ||     |
   |        |  |         |   |    |   __________||||      |       /      |    |    \/ 2     ||       |    |    \/ 2     || ||     |  |         |   |    |   __________||||      |       /      |    |    \/ 2     ||       |    |    \/ 2     || ||     |
   |        |  |         |   |    |  /      2/3 ||||      |      /       |atan|-------------||       |atan|-------------|| ||     |  |         |   |    |  /      2/3 ||||      |      /       |atan|-------------||       |atan|-------------|| ||     |
   |        |  |         |   |    \\/  4 - 2    /|||      |     /        |    |   __________||       |    |   __________|| ||     |  |         |   |    \\/  4 - 2    /|||      |     /        |    |   __________||       |    |   __________|| ||     |
   |        |  |         |sin|-------------------|||      |    /         |    |  /      2/3 ||       |    |  /      2/3 || ||     |  |         |cos|-------------------|||      |    /         |    |  /      2/3 ||       |    |  /      2/3 || ||     |
   |        |  |         |   \         2         /||      |   /         2|    \\/  4 - 2    /|      2|    \\/  4 - 2    /| ||     |  |         |   \         2         /||      |   /         2|    \\/  4 - 2    /|      2|    \\/  4 - 2    /| ||     |
And|x <= -I*|I*|pi - atan|------------------------|| + log|  /       cos |-------------------| + sin |-------------------| ||, -I*|I*|pi - atan|------------------------|| + log|  /       cos |-------------------| + sin |-------------------| || <= x|
   |        |  |         |   /    /    3 ___    \\||      \\/            \         2         /       \         2         / /|     |  |         |   /    /    3 ___    \\||      \\/            \         2         /       \         2         / /|     |
   |        |  |         |   |    |    \/ 2     ||||                                                                        |     |  |         |   |    |    \/ 2     ||||                                                                        |     |
   |        |  |         |   |atan|-------------||||                                                                        |     |  |         |   |atan|-------------||||                                                                        |     |
   |        |  |         |   |    |   __________||||                                                                        |     |  |         |   |    |   __________||||                                                                        |     |
   |        |  |         |   |    |  /      2/3 ||||                                                                        |     |  |         |   |    |  /      2/3 ||||                                                                        |     |
   |        |  |         |   |    \\/  4 - 2    /|||                                                                        |     |  |         |   |    \\/  4 - 2    /|||                                                                        |     |
   |        |  |         |cos|-------------------|||                                                                        |     |  |         |sin|-------------------|||                                                                        |     |
   \        \  \         \   \         2         ///                                                                        /     \  \         \   \         2         ///                                                                        /     /
$$x \leq - i \left(\log{\left(\sqrt{\sin^{2}{\left(\frac{\operatorname{atan}{\left(\frac{\sqrt[3]{2}}{\sqrt{4 - 2^{\frac{2}{3}}}} \right)}}{2} \right)} + \cos^{2}{\left(\frac{\operatorname{atan}{\left(\frac{\sqrt[3]{2}}{\sqrt{4 - 2^{\frac{2}{3}}}} \right)}}{2} \right)}} \right)} + i \left(\pi - \operatorname{atan}{\left(\frac{\sin{\left(\frac{\operatorname{atan}{\left(\frac{\sqrt[3]{2}}{\sqrt{4 - 2^{\frac{2}{3}}}} \right)}}{2} \right)}}{\cos{\left(\frac{\operatorname{atan}{\left(\frac{\sqrt[3]{2}}{\sqrt{4 - 2^{\frac{2}{3}}}} \right)}}{2} \right)}} \right)}\right)\right) \wedge - i \left(\log{\left(\sqrt{\sin^{2}{\left(\frac{\operatorname{atan}{\left(\frac{\sqrt[3]{2}}{\sqrt{4 - 2^{\frac{2}{3}}}} \right)}}{2} \right)} + \cos^{2}{\left(\frac{\operatorname{atan}{\left(\frac{\sqrt[3]{2}}{\sqrt{4 - 2^{\frac{2}{3}}}} \right)}}{2} \right)}} \right)} + i \left(\pi - \operatorname{atan}{\left(\frac{\cos{\left(\frac{\operatorname{atan}{\left(\frac{\sqrt[3]{2}}{\sqrt{4 - 2^{\frac{2}{3}}}} \right)}}{2} \right)}}{\sin{\left(\frac{\operatorname{atan}{\left(\frac{\sqrt[3]{2}}{\sqrt{4 - 2^{\frac{2}{3}}}} \right)}}{2} \right)}} \right)}\right)\right) \leq x$$
(x <= -i*(i*(pi - atan(sin(atan(2^(1/3)/sqrt(4 - 2^(2/3)))/2)/cos(atan(2^(1/3)/sqrt(4 - 2^(2/3)))/2))) + log(sqrt(cos(atan(2^(1/3)/sqrt(4 - 2^(2/3)))/2)^2 + sin(atan(2^(1/3)/sqrt(4 - 2^(2/3)))/2)^2))))∧(-i*(i*(pi - atan(cos(atan(2^(1/3)/sqrt(4 - 2^(2/3)))/2)/sin(atan(2^(1/3)/sqrt(4 - 2^(2/3)))/2))) + log(sqrt(cos(atan(2^(1/3)/sqrt(4 - 2^(2/3)))/2)^2 + sin(atan(2^(1/3)/sqrt(4 - 2^(2/3)))/2)^2))) <= x)