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(sin(x))^4+(cos(x))^4>=√3/2 desigualdades

En la desigualdad la incógnita

Solución

Ha introducido [src]
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   4         4       \/ 3 
sin (x) + cos (x) >= -----
                       2  
$$\sin^{4}{\left(x \right)} + \cos^{4}{\left(x \right)} \geq \frac{\sqrt{3}}{2}$$
sin(x)^4 + cos(x)^4 >= sqrt(3)/2
Solución detallada
Se da la desigualdad:
$$\sin^{4}{\left(x \right)} + \cos^{4}{\left(x \right)} \geq \frac{\sqrt{3}}{2}$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$\sin^{4}{\left(x \right)} + \cos^{4}{\left(x \right)} = \frac{\sqrt{3}}{2}$$
Resolvemos:
$$x_{1} = - 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)}$$
$$x_{2} = 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)}$$
$$x_{3} = - 2 \operatorname{atan}{\left(\sqrt{- 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}} + 4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}}} \right)}$$
$$x_{4} = 2 \operatorname{atan}{\left(\sqrt{- 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}} + 4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}}} \right)}$$
$$x_{5} = - 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} - 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{6} = 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} - 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{7} = - 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{8} = 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{1} = - 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)}$$
$$x_{2} = 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)}$$
$$x_{3} = - 2 \operatorname{atan}{\left(\sqrt{- 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}} + 4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}}} \right)}$$
$$x_{4} = 2 \operatorname{atan}{\left(\sqrt{- 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}} + 4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}}} \right)}$$
$$x_{5} = - 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} - 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{6} = 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} - 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{7} = - 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{8} = 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
Las raíces dadas
$$x_{1} = - 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)}$$
$$x_{7} = - 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{5} = - 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} - 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{3} = - 2 \operatorname{atan}{\left(\sqrt{- 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}} + 4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}}} \right)}$$
$$x_{4} = 2 \operatorname{atan}{\left(\sqrt{- 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}} + 4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}}} \right)}$$
$$x_{6} = 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} - 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{8} = 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x_{2} = 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)}$$
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
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)} - \frac{1}{10}$$
=
$$- 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)} - \frac{1}{10}$$
lo sustituimos en la expresión
$$\sin^{4}{\left(x \right)} + \cos^{4}{\left(x \right)} \geq \frac{\sqrt{3}}{2}$$
$$\sin^{4}{\left(- 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)} - \frac{1}{10} \right)} + \cos^{4}{\left(- 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)} - \frac{1}{10} \right)} \geq \frac{\sqrt{3}}{2}$$
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    |           |   /                     _____________              /           _____________                         _____________  ||       |           |   /                     _____________              /           _____________                         _____________  ||    \/ 3 
   4|1          |  /           ___       /         ___        ___   /           /         ___         ___       ___   /         ___   ||      4|1          |  /           ___       /         ___        ___   /           /         ___         ___       ___   /         ___   || >= -----
cos |-- + 2*atan\\/    7 + 4*\/ 3  + 4*\/  5 + 3*\/ 3   + 2*\/ 2 *\/   22 + 7*\/  5 + 3*\/ 3   + 13*\/ 3  + 4*\/ 3 *\/  5 + 3*\/ 3    /| + sin |-- + 2*atan\\/    7 + 4*\/ 3  + 4*\/  5 + 3*\/ 3   + 2*\/ 2 *\/   22 + 7*\/  5 + 3*\/ 3   + 13*\/ 3  + 4*\/ 3 *\/  5 + 3*\/ 3    /|      2  
    \10                                                                                                                                /       \10                                                                                                                                /    
         

significa que una de las soluciones de nuestra ecuación será con:
$$x \leq - 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)}$$
 _____           _____           _____           _____           _____          
      \         /     \         /     \         /     \         /
-------•-------•-------•-------•-------•-------•-------•-------•-------
       x1      x7      x5      x3      x4      x6      x8      x2

Recibiremos otras soluciones de la desigualdad pasando al polo siguiente etc.
etc.
Respuesta:
$$x \leq - 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)}$$
$$x \geq - 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)} \wedge x \leq - 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} - 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x \geq - 2 \operatorname{atan}{\left(\sqrt{- 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}} + 4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}}} \right)} \wedge x \leq 2 \operatorname{atan}{\left(\sqrt{- 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}} + 4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}}} \right)}$$
$$x \geq 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} - 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)} \wedge x \leq 2 \operatorname{atan}{\left(\sqrt{- 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{- 7 \sqrt{5 + 3 \sqrt{3}} - 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 22 + 13 \sqrt{3}} + 4 \sqrt{3} + 7} \right)}$$
$$x \geq 2 \operatorname{atan}{\left(\sqrt{4 \sqrt{3} + 7 + 4 \sqrt{5 + 3 \sqrt{3}} + 2 \sqrt{2} \sqrt{22 + 4 \sqrt{3} \sqrt{5 + 3 \sqrt{3}} + 7 \sqrt{5 + 3 \sqrt{3}} + 13 \sqrt{3}}} \right)}$$
Solución de la desigualdad en el gráfico