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cos(2*x)+1/2=cos(x)^2 la ecuación

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Solución numérica:

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Solución

Ha introducido [src]
                    2   
cos(2*x) + 1/2 = cos (x)
$$\cos{\left(2 x \right)} + \frac{1}{2} = \cos^{2}{\left(x \right)}$$
Solución detallada
Tenemos la ecuación
$$\cos{\left(2 x \right)} + \frac{1}{2} = \cos^{2}{\left(x \right)}$$
cambiamos
$$\frac{\cos{\left(2 x \right)}}{2} = 0$$
$$\cos^{2}{\left(x \right)} - \frac{1}{2} = 0$$
Sustituimos
$$w = \cos{\left(x \right)}$$
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
$$a = 1$$
$$b = 0$$
$$c = - \frac{1}{2}$$
, entonces
D = b^2 - 4 * a * c = 

(0)^2 - 4 * (1) * (-1/2) = 2

Como D > 0 la ecuación tiene dos raíces.
w1 = (-b + sqrt(D)) / (2*a)

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

o
$$w_{1} = \frac{\sqrt{2}}{2}$$
$$w_{2} = - \frac{\sqrt{2}}{2}$$
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:
$$x_{1} = \pi n + \operatorname{acos}{\left(w_{1} \right)}$$
$$x_{1} = \pi n + \operatorname{acos}{\left(\frac{\sqrt{2}}{2} \right)}$$
$$x_{1} = \pi n + \frac{\pi}{4}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(w_{2} \right)}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(- \frac{\sqrt{2}}{2} \right)}$$
$$x_{2} = \pi n + \frac{3 \pi}{4}$$
$$x_{3} = \pi n + \operatorname{acos}{\left(w_{1} \right)} - \pi$$
$$x_{3} = \pi n - \pi + \operatorname{acos}{\left(\frac{\sqrt{2}}{2} \right)}$$
$$x_{3} = \pi n - \frac{3 \pi}{4}$$
$$x_{4} = \pi n + \operatorname{acos}{\left(w_{2} \right)} - \pi$$
$$x_{4} = \pi n - \pi + \operatorname{acos}{\left(- \frac{\sqrt{2}}{2} \right)}$$
$$x_{4} = \pi n - \frac{\pi}{4}$$
Gráfica
Suma y producto de raíces [src]
suma
  3*pi   pi   pi   3*pi
- ---- - -- + -- + ----
   4     4    4     4  
$$\left(\left(- \frac{3 \pi}{4} - \frac{\pi}{4}\right) + \frac{\pi}{4}\right) + \frac{3 \pi}{4}$$
=
0
$$0$$
producto
-3*pi -pi  pi 3*pi
-----*----*--*----
  4    4   4   4  
$$\frac{3 \pi}{4} \frac{\pi}{4} \cdot - \frac{3 \pi}{4} \left(- \frac{\pi}{4}\right)$$
=
    4
9*pi 
-----
 256 
$$\frac{9 \pi^{4}}{256}$$
9*pi^4/256
Respuesta rápida [src]
     -3*pi
x1 = -----
       4  
$$x_{1} = - \frac{3 \pi}{4}$$
     -pi 
x2 = ----
      4  
$$x_{2} = - \frac{\pi}{4}$$
     pi
x3 = --
     4 
$$x_{3} = \frac{\pi}{4}$$
     3*pi
x4 = ----
      4  
$$x_{4} = \frac{3 \pi}{4}$$
x4 = 3*pi/4
Respuesta numérica [src]
x1 = -5.49778714378214
x2 = -38.484510006475
x3 = -40.0553063332699
x4 = 30.6305283725005
x5 = 84.037603483527
x6 = 85.6083998103219
x7 = 54.1924732744239
x8 = -68.329640215578
x9 = 19.6349540849362
x10 = 11.7809724509617
x11 = 858.440192593411
x12 = 68.329640215578
x13 = 44.7676953136546
x14 = -54.1924732744239
x15 = -47.9092879672443
x16 = -18.0641577581413
x17 = -16.4933614313464
x18 = 90.3207887907066
x19 = 8.63937979737193
x20 = -84.037603483527
x21 = -69.9004365423729
x22 = -19.6349540849362
x23 = 49.4800842940392
x24 = -27.4889357189107
x25 = -3.92699081698724
x26 = 41.6261026600648
x27 = -55.7632696012188
x28 = -76.1836218495525
x29 = 62.0464549083984
x30 = -32.2013246992954
x31 = -46.3384916404494
x32 = 25.9181393921158
x33 = -77.7544181763474
x34 = 47.9092879672443
x35 = 91.8915851175014
x36 = 24.3473430653209
x37 = 38.484510006475
x38 = 99.7455667514759
x39 = 40.0553063332699
x40 = 66.7588438887831
x41 = 384.059701901352
x42 = -13.3517687777566
x43 = 88.7499924639117
x44 = 98.174770424681
x45 = 10.2101761241668
x46 = -90.3207887907066
x47 = 3326.16122198819
x48 = 55.7632696012188
x49 = -49.4800842940392
x50 = 22.776546738526
x51 = -79.3252145031423
x52 = 60.4756585816035
x53 = 74.6128255227576
x54 = -99.7455667514759
x55 = -24.3473430653209
x56 = -71.4712328691678
x57 = 76.1836218495525
x58 = 3.92699081698724
x59 = -62.0464549083984
x60 = -33.7721210260903
x61 = 18.0641577581413
x62 = -41.6261026600648
x63 = 162.577419823272
x64 = -85.6083998103219
x65 = -35.3429173528852
x66 = 87.1791961371168
x67 = 52.621676947629
x68 = 69.9004365423729
x69 = 96.6039740978861
x70 = -82.4668071567321
x71 = -63.6172512351933
x72 = -11.7809724509617
x73 = 27.4889357189107
x74 = -10.2101761241668
x75 = 82.4668071567321
x76 = 46.3384916404494
x77 = -1144.32512407008
x78 = -93.4623814442964
x79 = -60.4756585816035
x80 = -91.8915851175014
x81 = 32.2013246992954
x82 = -98.174770424681
x83 = -2.35619449019234
x84 = 63.6172512351933
x85 = 5.49778714378214
x86 = -57.3340659280137
x87 = 77.7544181763474
x88 = -25.9181393921158
x89 = 16.4933614313464
x90 = 2.35619449019234
x91 = 33.7721210260903
x91 = 33.7721210260903