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3*cos(-4*x+pi/9)>-3*sqrt(3)/2 desigualdades

En la desigualdad la incógnita

Solución

Ha introducido [src]
                        ___
     /       pi\   -3*\/ 3 
3*cos|-4*x + --| > --------
     \       9 /      2    
$$3 \cos{\left(- 4 x + \frac{\pi}{9} \right)} > \frac{\left(-1\right) 3 \sqrt{3}}{2}$$
3*cos(-4*x + pi/9) > (-3*sqrt(3))/2
Solución detallada
Se da la desigualdad:
$$3 \cos{\left(- 4 x + \frac{\pi}{9} \right)} > \frac{\left(-1\right) 3 \sqrt{3}}{2}$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$3 \cos{\left(- 4 x + \frac{\pi}{9} \right)} = \frac{\left(-1\right) 3 \sqrt{3}}{2}$$
Resolvemos:
Tenemos la ecuación
$$3 \cos{\left(- 4 x + \frac{\pi}{9} \right)} = \frac{\left(-1\right) 3 \sqrt{3}}{2}$$
es la ecuación trigonométrica más simple
Dividamos ambos miembros de la ecuación en 3

La ecuación se convierte en
$$\sin{\left(4 x + \frac{7 \pi}{18} \right)} = - \frac{\sqrt{3}}{2}$$
Esta ecuación se reorganiza en
$$4 x + \frac{7 \pi}{18} = 2 \pi n + \operatorname{asin}{\left(- \frac{\sqrt{3}}{2} \right)}$$
$$4 x + \frac{7 \pi}{18} = 2 \pi n - \operatorname{asin}{\left(- \frac{\sqrt{3}}{2} \right)} + \pi$$
O
$$4 x + \frac{7 \pi}{18} = 2 \pi n - \frac{\pi}{3}$$
$$4 x + \frac{7 \pi}{18} = 2 \pi n + \frac{4 \pi}{3}$$
, donde n es cualquier número entero
Transportemos
$$\frac{7 \pi}{18}$$
al miembro derecho de la ecuación
con el signo opuesto, en total:
$$4 x = 2 \pi n - \frac{13 \pi}{18}$$
$$4 x = 2 \pi n + \frac{17 \pi}{18}$$
Dividamos ambos miembros de la ecuación obtenida en
$$4$$
$$x_{1} = \frac{\pi n}{2} - \frac{13 \pi}{72}$$
$$x_{2} = \frac{\pi n}{2} + \frac{17 \pi}{72}$$
$$x_{1} = \frac{\pi n}{2} - \frac{13 \pi}{72}$$
$$x_{2} = \frac{\pi n}{2} + \frac{17 \pi}{72}$$
Las raíces dadas
$$x_{1} = \frac{\pi n}{2} - \frac{13 \pi}{72}$$
$$x_{2} = \frac{\pi n}{2} + \frac{17 \pi}{72}$$
son puntos de cambio del signo de desigualdad en las soluciones.
Primero definámonos con el signo hasta el punto extremo izquierdo:
$$x_{0} < x_{1}$$
Consideremos, por ejemplo, el punto
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$\left(\frac{\pi n}{2} - \frac{13 \pi}{72}\right) + - \frac{1}{10}$$
=
$$\frac{\pi n}{2} - \frac{13 \pi}{72} - \frac{1}{10}$$
lo sustituimos en la expresión
$$3 \cos{\left(- 4 x + \frac{\pi}{9} \right)} > \frac{\left(-1\right) 3 \sqrt{3}}{2}$$
$$3 \cos{\left(- 4 \left(\frac{\pi n}{2} - \frac{13 \pi}{72} - \frac{1}{10}\right) + \frac{\pi}{9} \right)} > \frac{\left(-1\right) 3 \sqrt{3}}{2}$$
                               ___
      /2   pi         \   -3*\/ 3 
-3*sin|- + -- - 2*pi*n| > --------
      \5   3          /      2    
                          

Entonces
$$x < \frac{\pi n}{2} - \frac{13 \pi}{72}$$
no se cumple
significa que una de las soluciones de nuestra ecuación será con:
$$x > \frac{\pi n}{2} - \frac{13 \pi}{72} \wedge x < \frac{\pi n}{2} + \frac{17 \pi}{72}$$
         _____  
        /     \  
-------ο-------ο-------
       x1      x2
Solución de la desigualdad en el gráfico
Respuesta rápida [src]
  /   /                 /       3/7*pi\       ___        /7*pi\       ___    4/7*pi\                      2/7*pi\            \ \     /                  /       3/7*pi\       ___        /7*pi\       ___    4/7*pi\                      2/7*pi\            \    \\
  |   |                 |- 8*tan |----| + 2*\/ 3  + 8*tan|----| - 2*\/ 3 *tan |----|               1 + tan |----|            | |     |                  |- 8*tan |----| + 2*\/ 3  + 8*tan|----| - 2*\/ 3 *tan |----|               1 + tan |----|            |    ||
  |   |                 |        \ 36 /                  \ 36 /               \ 36 /                       \ 36 /            | |     |                  |        \ 36 /                  \ 36 /               \ 36 /                       \ 36 /            |    ||
  |   |            -atan|----------------------------------------------------------- + --------------------------------------| |     |              atan|----------------------------------------------------------- - --------------------------------------|    ||
  |   |                 |                        2/7*pi\        4/7*pi\                  ___        /7*pi\     ___    2/7*pi\| |     |                  |                        2/7*pi\        4/7*pi\                  ___        /7*pi\     ___    2/7*pi\|    ||
  |   |                 |              3 - 10*tan |----| + 3*tan |----|                \/ 3  - 4*tan|----| + \/ 3 *tan |----|| |     |                  |              3 - 10*tan |----| + 3*tan |----|                \/ 3  - 4*tan|----| + \/ 3 *tan |----||    ||
  |   |                 \                         \ 36 /         \ 36 /                             \ 36 /             \ 36 // |     |     pi  pi       \                         \ 36 /         \ 36 /                             \ 36 /             \ 36 //    ||
Or|And|0 <= x, x < ------------------------------------------------------------------------------------------------------------|, And|x <= --, -- - ---------------------------------------------------------------------------------------------------------- < x||
  \   \                                                                 2                                                      /     \     2   2                                                        2                                                         //
$$\left(0 \leq x \wedge x < - \frac{\operatorname{atan}{\left(\frac{\tan^{2}{\left(\frac{7 \pi}{36} \right)} + 1}{- 4 \tan{\left(\frac{7 \pi}{36} \right)} + \sqrt{3} \tan^{2}{\left(\frac{7 \pi}{36} \right)} + \sqrt{3}} + \frac{- 8 \tan^{3}{\left(\frac{7 \pi}{36} \right)} - 2 \sqrt{3} \tan^{4}{\left(\frac{7 \pi}{36} \right)} + 2 \sqrt{3} + 8 \tan{\left(\frac{7 \pi}{36} \right)}}{- 10 \tan^{2}{\left(\frac{7 \pi}{36} \right)} + 3 \tan^{4}{\left(\frac{7 \pi}{36} \right)} + 3} \right)}}{2}\right) \vee \left(x \leq \frac{\pi}{2} \wedge - \frac{\operatorname{atan}{\left(\frac{- 8 \tan^{3}{\left(\frac{7 \pi}{36} \right)} - 2 \sqrt{3} \tan^{4}{\left(\frac{7 \pi}{36} \right)} + 2 \sqrt{3} + 8 \tan{\left(\frac{7 \pi}{36} \right)}}{- 10 \tan^{2}{\left(\frac{7 \pi}{36} \right)} + 3 \tan^{4}{\left(\frac{7 \pi}{36} \right)} + 3} - \frac{\tan^{2}{\left(\frac{7 \pi}{36} \right)} + 1}{- 4 \tan{\left(\frac{7 \pi}{36} \right)} + \sqrt{3} \tan^{2}{\left(\frac{7 \pi}{36} \right)} + \sqrt{3}} \right)}}{2} + \frac{\pi}{2} < x\right)$$
((0 <= x)∧(x < -atan((-8*tan(7*pi/36)^3 + 2*sqrt(3) + 8*tan(7*pi/36) - 2*sqrt(3)*tan(7*pi/36)^4)/(3 - 10*tan(7*pi/36)^2 + 3*tan(7*pi/36)^4) + (1 + tan(7*pi/36)^2)/(sqrt(3) - 4*tan(7*pi/36) + sqrt(3)*tan(7*pi/36)^2))/2))∨((x <= pi/2)∧(pi/2 - atan((-8*tan(7*pi/36)^3 + 2*sqrt(3) + 8*tan(7*pi/36) - 2*sqrt(3)*tan(7*pi/36)^4)/(3 - 10*tan(7*pi/36)^2 + 3*tan(7*pi/36)^4) - (1 + tan(7*pi/36)^2)/(sqrt(3) - 4*tan(7*pi/36) + sqrt(3)*tan(7*pi/36)^2))/2 < x))
Respuesta rápida 2 [src]
         /       3/7*pi\       ___        /7*pi\       ___    4/7*pi\                      2/7*pi\            \               /       3/7*pi\       ___        /7*pi\       ___    4/7*pi\                      2/7*pi\            \     
         |- 8*tan |----| + 2*\/ 3  + 8*tan|----| - 2*\/ 3 *tan |----|               1 + tan |----|            |               |- 8*tan |----| + 2*\/ 3  + 8*tan|----| - 2*\/ 3 *tan |----|               1 + tan |----|            |     
         |        \ 36 /                  \ 36 /               \ 36 /                       \ 36 /            |               |        \ 36 /                  \ 36 /               \ 36 /                       \ 36 /            |     
    -atan|----------------------------------------------------------- + --------------------------------------|           atan|----------------------------------------------------------- - --------------------------------------|     
         |                        2/7*pi\        4/7*pi\                  ___        /7*pi\     ___    2/7*pi\|               |                        2/7*pi\        4/7*pi\                  ___        /7*pi\     ___    2/7*pi\|     
         |              3 - 10*tan |----| + 3*tan |----|                \/ 3  - 4*tan|----| + \/ 3 *tan |----||               |              3 - 10*tan |----| + 3*tan |----|                \/ 3  - 4*tan|----| + \/ 3 *tan |----||     
         \                         \ 36 /         \ 36 /                             \ 36 /             \ 36 //      pi       \                         \ 36 /         \ 36 /                             \ 36 /             \ 36 //  pi 
[0, ------------------------------------------------------------------------------------------------------------) U (-- - ----------------------------------------------------------------------------------------------------------, --]
                                                         2                                                           2                                                        2                                                       2  
$$x\ in\ \left[0, - \frac{\operatorname{atan}{\left(\frac{\tan^{2}{\left(\frac{7 \pi}{36} \right)} + 1}{- 4 \tan{\left(\frac{7 \pi}{36} \right)} + \sqrt{3} \tan^{2}{\left(\frac{7 \pi}{36} \right)} + \sqrt{3}} + \frac{- 8 \tan^{3}{\left(\frac{7 \pi}{36} \right)} - 2 \sqrt{3} \tan^{4}{\left(\frac{7 \pi}{36} \right)} + 2 \sqrt{3} + 8 \tan{\left(\frac{7 \pi}{36} \right)}}{- 10 \tan^{2}{\left(\frac{7 \pi}{36} \right)} + 3 \tan^{4}{\left(\frac{7 \pi}{36} \right)} + 3} \right)}}{2}\right) \cup \left(- \frac{\operatorname{atan}{\left(\frac{- 8 \tan^{3}{\left(\frac{7 \pi}{36} \right)} - 2 \sqrt{3} \tan^{4}{\left(\frac{7 \pi}{36} \right)} + 2 \sqrt{3} + 8 \tan{\left(\frac{7 \pi}{36} \right)}}{- 10 \tan^{2}{\left(\frac{7 \pi}{36} \right)} + 3 \tan^{4}{\left(\frac{7 \pi}{36} \right)} + 3} - \frac{\tan^{2}{\left(\frac{7 \pi}{36} \right)} + 1}{- 4 \tan{\left(\frac{7 \pi}{36} \right)} + \sqrt{3} \tan^{2}{\left(\frac{7 \pi}{36} \right)} + \sqrt{3}} \right)}}{2} + \frac{\pi}{2}, \frac{\pi}{2}\right]$$
x in Union(Interval.Ropen(0, -atan((tan(7*pi/36)^2 + 1)/(-4*tan(7*pi/36) + sqrt(3)*tan(7*pi/36)^2 + sqrt(3)) + (-8*tan(7*pi/36)^3 - 2*sqrt(3)*tan(7*pi/36)^4 + 2*sqrt(3) + 8*tan(7*pi/36))/(-10*tan(7*pi/36)^2 + 3*tan(7*pi/36)^4 + 3))/2), Interval.Lopen(-atan((-8*tan(7*pi/36)^3 - 2*sqrt(3)*tan(7*pi/36)^4 + 2*sqrt(3) + 8*tan(7*pi/36))/(-10*tan(7*pi/36)^2 + 3*tan(7*pi/36)^4 + 3) - (tan(7*pi/36)^2 + 1)/(-4*tan(7*pi/36) + sqrt(3)*tan(7*pi/36)^2 + sqrt(3)))/2 + pi/2, pi/2))