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sqrt(-cos(2*x))+(sqrt(2))*cos(x)=0 la ecuación

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Solución numérica:

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Solución

Ha introducido [src]
  ___________     ___           
\/ -cos(2*x)  + \/ 2 *cos(x) = 0
$$\sqrt{- \cos{\left(2 x \right)}} + \sqrt{2} \cos{\left(x \right)} = 0$$
Solución detallada
Tenemos la ecuación
$$\sqrt{- \cos{\left(2 x \right)}} + \sqrt{2} \cos{\left(x \right)} = 0$$
cambiamos
$$\sqrt{2} \sqrt{- \cos^{2}{\left(x \right)}} + \sqrt{2} \cos{\left(x \right)} - 1 = 0$$
$$\sqrt{2} \sqrt{- \cos^{2}{\left(x \right)}} + \sqrt{2} \cos{\left(x \right)} - 1 = 0$$
Sustituimos
$$w = \cos{\left(x \right)}$$
$$\sqrt{2} \sqrt{- w^{2}} = - \sqrt{2} w + 1$$
Elevemos las dos partes de la ecuación a la potencia 2
$$- 2 w^{2} = \left(- \sqrt{2} w + 1\right)^{2}$$
$$- 2 w^{2} = 2 w^{2} - 2 \sqrt{2} w + 1$$
Transpongamos la parte derecha de la ecuación miembro izquierdo de la ecuación con el signo negativo
$$- 4 w^{2} + 2 \sqrt{2} w - 1 = 0$$
Es la ecuación de la forma
a*w^2 + b*w + c = 0

La ecuación cuadrática puede ser resuelta
con la ayuda del discriminante.
Las raíces de la ecuación cuadrática:
$$w_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$w_{2} = \frac{- \sqrt{D} - b}{2 a}$$
donde D = b^2 - 4*a*c es el discriminante.
Como
$$a = -4$$
$$b = 2 \sqrt{2}$$
$$c = -1$$
, entonces
D = b^2 - 4 * a * c = 

(2*sqrt(2))^2 - 4 * (-4) * (-1) = -8

Como D < 0 la ecuación
no tiene raíces reales,
pero hay raíces complejas.
w1 = (-b + sqrt(D)) / (2*a)

w2 = (-b - sqrt(D)) / (2*a)

o
$$w_{1} = \frac{\sqrt{2}}{4} - \frac{\sqrt{2} i}{4}$$
$$w_{2} = \frac{\sqrt{2}}{4} + \frac{\sqrt{2} i}{4}$$
hacemos cambio inverso
$$\cos{\left(x \right)} = w$$
Tenemos la ecuación
$$\cos{\left(x \right)} = w$$
es la ecuación trigonométrica más simple
Esta ecuación se reorganiza en
$$x = \pi n + \operatorname{acos}{\left(w \right)}$$
$$x = \pi n + \operatorname{acos}{\left(w \right)} - \pi$$
O
$$x = \pi n + \operatorname{acos}{\left(w \right)}$$
$$x = \pi n + \operatorname{acos}{\left(w \right)} - \pi$$
, donde n es cualquier número entero
sustituimos w:
$$x_{1} = \pi n + \operatorname{acos}{\left(w_{1} \right)}$$
$$x_{1} = \pi n + \operatorname{acos}{\left(\frac{\sqrt{2}}{4} - \frac{\sqrt{2} i}{4} \right)}$$
$$x_{1} = \pi n + \operatorname{acos}{\left(\frac{\sqrt{2}}{4} - \frac{\sqrt{2} i}{4} \right)}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(w_{2} \right)}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(\frac{\sqrt{2}}{4} + \frac{\sqrt{2} i}{4} \right)}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(\frac{\sqrt{2}}{4} + \frac{\sqrt{2} i}{4} \right)}$$
$$x_{3} = \pi n + \operatorname{acos}{\left(w_{1} \right)} - \pi$$
$$x_{3} = \pi n - \pi + \operatorname{acos}{\left(\frac{\sqrt{2}}{4} - \frac{\sqrt{2} i}{4} \right)}$$
$$x_{3} = \pi n - \pi + \operatorname{acos}{\left(\frac{\sqrt{2}}{4} - \frac{\sqrt{2} i}{4} \right)}$$
$$x_{4} = \pi n + \operatorname{acos}{\left(w_{2} \right)} - \pi$$
$$x_{4} = \pi n - \pi + \operatorname{acos}{\left(\frac{\sqrt{2}}{4} + \frac{\sqrt{2} i}{4} \right)}$$
$$x_{4} = \pi n - \pi + \operatorname{acos}{\left(\frac{\sqrt{2}}{4} + \frac{\sqrt{2} i}{4} \right)}$$
Gráfica
Suma y producto de raíces [src]
suma
  2*pi   2*pi
- ---- + ----
   3      3  
$$- \frac{2 \pi}{3} + \frac{2 \pi}{3}$$
=
0
$$0$$
producto
-2*pi 2*pi
-----*----
  3    3  
$$- \frac{2 \pi}{3} \frac{2 \pi}{3}$$
=
     2
-4*pi 
------
  9   
$$- \frac{4 \pi^{2}}{9}$$
-4*pi^2/9
Respuesta rápida [src]
     -2*pi
x1 = -----
       3  
$$x_{1} = - \frac{2 \pi}{3}$$
     2*pi
x2 = ----
      3  
$$x_{2} = \frac{2 \pi}{3}$$
x2 = 2*pi/3
Respuesta numérica [src]
x1 = -29.3215314335047
x2 = -27.2271363311115
x3 = 39.7935069454707
x4 = -39.7935069454707
x5 = -20.943951023932
x6 = 4.18879020478639
x7 = -52.3598775598299
x8 = -73.3038285837618
x9 = 96.342174710087
x10 = 54.4542726622231
x11 = -140.324471860344
x12 = -54.4542726622231
x13 = -35.6047167406843
x14 = -77.4926187885482
x15 = 73.3038285837618
x16 = 16.7551608191456
x17 = -98.4365698124802
x18 = 77.4926187885482
x19 = -4.18879020478639
x20 = -14.6607657167524
x21 = 33.5103216382911
x22 = 41.8879020478639
x23 = 71.2094334813686
x24 = -33.5103216382911
x25 = 83.7758040957278
x26 = -48.1710873550435
x27 = 64.9262481741891
x28 = 10.471975511966
x29 = 67.0206432765823
x30 = 52.3598775598299
x31 = -41.8879020478639
x32 = -67.0206432765823
x33 = 46.0766922526503
x34 = 85.870199198121
x35 = 60.7374579694027
x36 = -46.0766922526503
x37 = -23.0383461263252
x38 = -83.7758040957278
x39 = -16.7551608191456
x40 = 20.943951023932
x41 = -90.0589894029074
x42 = -58.6430628670095
x43 = -85.870199198121
x44 = -10.471975511966
x45 = 79.5870138909414
x46 = 92.1533845053006
x47 = -8.37758040957278
x48 = 14.6607657167524
x49 = 48.1710873550435
x50 = -60.7374579694027
x51 = 8.37758040957278
x52 = -2.0943951023932
x53 = 90.0589894029074
x54 = 29.3215314335047
x55 = 35.6047167406843
x56 = -79.5870138909414
x57 = 98.4365698124802
x58 = 23.0383461263252
x59 = 58.6430628670095
x60 = -92.1533845053006
x61 = -96.342174710087
x62 = 2.0943951023932
x63 = -71.2094334813686
x64 = 27.2271363311115
x64 = 27.2271363311115