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cos(x)^(2)=3/4

cos(x)^(2)=3/4 la ecuación

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Solución numérica:

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Solución

Ha introducido [src]
   2         
cos (x) = 3/4
$$\cos^{2}{\left(x \right)} = \frac{3}{4}$$
Solución detallada
Tenemos la ecuación
$$\cos^{2}{\left(x \right)} = \frac{3}{4}$$
cambiamos
$$\cos^{2}{\left(x \right)} - \frac{3}{4} = 0$$
$$\cos^{2}{\left(x \right)} - \frac{3}{4} = 0$$
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
$$a = 1$$
$$b = 0$$
$$c = - \frac{3}{4}$$
, entonces
D = b^2 - 4 * a * c = 

(0)^2 - 4 * (1) * (-3/4) = 3

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

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

o
$$w_{1} = \frac{\sqrt{3}}{2}$$
$$w_{2} = - \frac{\sqrt{3}}{2}$$
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:
$$x_{1} = \pi n + \operatorname{acos}{\left(w_{1} \right)}$$
$$x_{1} = \pi n + \operatorname{acos}{\left(\frac{\sqrt{3}}{2} \right)}$$
$$x_{1} = \pi n + \frac{\pi}{6}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(w_{2} \right)}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(- \frac{\sqrt{3}}{2} \right)}$$
$$x_{2} = \pi n + \frac{5 \pi}{6}$$
$$x_{3} = \pi n + \operatorname{acos}{\left(w_{1} \right)} - \pi$$
$$x_{3} = \pi n - \pi + \operatorname{acos}{\left(\frac{\sqrt{3}}{2} \right)}$$
$$x_{3} = \pi n - \frac{5 \pi}{6}$$
$$x_{4} = \pi n + \operatorname{acos}{\left(w_{2} \right)} - \pi$$
$$x_{4} = \pi n - \pi + \operatorname{acos}{\left(- \frac{\sqrt{3}}{2} \right)}$$
$$x_{4} = \pi n - \frac{\pi}{6}$$
Gráfica
Suma y producto de raíces [src]
suma
pi   5*pi   7*pi   11*pi
-- + ---- + ---- + -----
6     6      6       6  
$$\frac{11 \pi}{6} + \left(\left(\frac{\pi}{6} + \frac{5 \pi}{6}\right) + \frac{7 \pi}{6}\right)$$
=
4*pi
$$4 \pi$$
producto
pi 5*pi 7*pi 11*pi
--*----*----*-----
6   6    6     6  
$$\frac{11 \pi}{6} \frac{7 \pi}{6} \frac{\pi}{6} \frac{5 \pi}{6}$$
=
      4
385*pi 
-------
  1296 
$$\frac{385 \pi^{4}}{1296}$$
385*pi^4/1296
Respuesta rápida [src]
     pi
x1 = --
     6 
$$x_{1} = \frac{\pi}{6}$$
     5*pi
x2 = ----
      6  
$$x_{2} = \frac{5 \pi}{6}$$
     7*pi
x3 = ----
      6  
$$x_{3} = \frac{7 \pi}{6}$$
     11*pi
x4 = -----
       6  
$$x_{4} = \frac{11 \pi}{6}$$
x4 = 11*pi/6
Respuesta numérica [src]
x1 = -3.66519142918809
x2 = 38.2227106186758
x3 = 88.4881930761125
x4 = 5.75958653158129
x5 = -82.2050077689329
x6 = 131.423292675173
x7 = 97.9129710368819
x8 = -68.5914396033772
x9 = 68.5914396033772
x10 = 30.8923277602996
x11 = 96.8657734856853
x12 = -9.94837673636768
x13 = -46.6002910282486
x14 = -56.025068989018
x15 = -24.60914245312
x16 = -2686.58531759487
x17 = -16.2315620435473
x18 = 60.2138591938044
x19 = 25.6563400043166
x20 = -84.2994028713261
x21 = -97.9129710368819
x22 = -53.9306738866248
x23 = -19.3731546971371
x24 = 62.3082542961976
x25 = -100.007366139275
x26 = 49.7418836818384
x27 = 24.60914245312
x28 = -75.9218224617533
x29 = 90.5825881785057
x30 = 66.497044500984
x31 = 93.7241808320955
x32 = -81.1578102177363
x33 = -78.0162175641465
x34 = -35.081117965086
x35 = -91.6297857297023
x36 = 100.007366139275
x37 = 34.0339204138894
x38 = -63.3554518473942
x39 = 69.6386371545737
x40 = 91.6297857297023
x41 = 53.9306738866248
x42 = 2.61799387799149
x43 = -85.3466004225227
x44 = -69.6386371545737
x45 = 125.140107367993
x46 = 12.0427718387609
x47 = 74.8746249105567
x48 = -12.0427718387609
x49 = 82.2050077689329
x50 = -21.4675497995303
x51 = -47.6474885794452
x52 = -13.0899693899575
x53 = 41.3643032722656
x54 = 9.94837673636768
x55 = 75.9218224617533
x56 = -49.7418836818384
x57 = 56.025068989018
x58 = 44.5058959258554
x59 = 27.7507351067098
x60 = -93.7241808320955
x61 = -43.4586983746588
x62 = 52.8834763354282
x63 = 63.3554518473942
x64 = 19.3731546971371
x65 = -71.733032256967
x66 = 3.66519142918809
x67 = -87.4409955249159
x68 = -40.317105721069
x69 = 46.6002910282486
x70 = 78.0162175641465
x71 = 0.523598775598299
x72 = 18.3259571459405
x73 = -25.6563400043166
x74 = 31.9395253114962
x75 = 47.6474885794452
x76 = -5.75958653158129
x77 = -90.5825881785057
x78 = -27.7507351067098
x79 = -34.0339204138894
x80 = -65.4498469497874
x81 = 8.90117918517108
x82 = -62.3082542961976
x83 = -18.3259571459405
x84 = -41.3643032722656
x85 = -31.9395253114962
x86 = 22.5147473507269
x87 = 84.2994028713261
x88 = 16.2315620435473
x89 = -60.2138591938044
x90 = -313.635666583381
x91 = -38.2227106186758
x92 = 40.317105721069
x93 = 85.3466004225227
x94 = -217.293491873294
x95 = 71.733032256967
x96 = -2.61799387799149
x96 = -2.61799387799149
Gráfico
cos(x)^(2)=3/4 la ecuación