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cos^2(x)=1/16 la ecuación

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Solución numérica:

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Solución

Ha introducido [src]
   2          
cos (x) = 1/16
$$\cos^{2}{\left(x \right)} = \frac{1}{16}$$
Solución detallada
Tenemos la ecuación
$$\cos^{2}{\left(x \right)} = \frac{1}{16}$$
cambiamos
$$\cos^{2}{\left(x \right)} - \frac{1}{16} = 0$$
$$\cos^{2}{\left(x \right)} - \frac{1}{16} = 0$$
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
$$a = 1$$
$$b = 0$$
$$c = - \frac{1}{16}$$
, entonces
D = b^2 - 4 * a * c = 

(0)^2 - 4 * (1) * (-1/16) = 1/4

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

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

o
$$w_{1} = \frac{1}{4}$$
$$w_{2} = - \frac{1}{4}$$
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:
$$x_{1} = \pi n + \operatorname{acos}{\left(w_{1} \right)}$$
$$x_{1} = \pi n + \operatorname{acos}{\left(\frac{1}{4} \right)}$$
$$x_{1} = \pi n + \operatorname{acos}{\left(\frac{1}{4} \right)}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(w_{2} \right)}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(- \frac{1}{4} \right)}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(- \frac{1}{4} \right)}$$
$$x_{3} = \pi n + \operatorname{acos}{\left(w_{1} \right)} - \pi$$
$$x_{3} = \pi n - \pi + \operatorname{acos}{\left(\frac{1}{4} \right)}$$
$$x_{3} = \pi n - \pi + \operatorname{acos}{\left(\frac{1}{4} \right)}$$
$$x_{4} = \pi n + \operatorname{acos}{\left(w_{2} \right)} - \pi$$
$$x_{4} = \pi n - \pi + \operatorname{acos}{\left(- \frac{1}{4} \right)}$$
$$x_{4} = \pi n - \pi + \operatorname{acos}{\left(- \frac{1}{4} \right)}$$
Gráfica
Suma y producto de raíces [src]
suma
-acos(-1/4) + 2*pi + -acos(1/4) + 2*pi + acos(-1/4) + acos(1/4)
$$\operatorname{acos}{\left(\frac{1}{4} \right)} + \left(\operatorname{acos}{\left(- \frac{1}{4} \right)} + \left(\left(- \operatorname{acos}{\left(- \frac{1}{4} \right)} + 2 \pi\right) + \left(- \operatorname{acos}{\left(\frac{1}{4} \right)} + 2 \pi\right)\right)\right)$$
=
4*pi
$$4 \pi$$
producto
(-acos(-1/4) + 2*pi)*(-acos(1/4) + 2*pi)*acos(-1/4)*acos(1/4)
$$\left(- \operatorname{acos}{\left(- \frac{1}{4} \right)} + 2 \pi\right) \left(- \operatorname{acos}{\left(\frac{1}{4} \right)} + 2 \pi\right) \operatorname{acos}{\left(- \frac{1}{4} \right)} \operatorname{acos}{\left(\frac{1}{4} \right)}$$
=
(-acos(-1/4) + 2*pi)*(-acos(1/4) + 2*pi)*acos(-1/4)*acos(1/4)
$$\left(- \operatorname{acos}{\left(- \frac{1}{4} \right)} + 2 \pi\right) \left(- \operatorname{acos}{\left(\frac{1}{4} \right)} + 2 \pi\right) \operatorname{acos}{\left(- \frac{1}{4} \right)} \operatorname{acos}{\left(\frac{1}{4} \right)}$$
(-acos(-1/4) + 2*pi)*(-acos(1/4) + 2*pi)*acos(-1/4)*acos(1/4)
Respuesta rápida [src]
x1 = -acos(-1/4) + 2*pi
$$x_{1} = - \operatorname{acos}{\left(- \frac{1}{4} \right)} + 2 \pi$$
x2 = -acos(1/4) + 2*pi
$$x_{2} = - \operatorname{acos}{\left(\frac{1}{4} \right)} + 2 \pi$$
x3 = acos(-1/4)
$$x_{3} = \operatorname{acos}{\left(- \frac{1}{4} \right)}$$
x4 = acos(1/4)
$$x_{4} = \operatorname{acos}{\left(\frac{1}{4} \right)}$$
x4 = acos(1/4)
Respuesta numérica [src]
x1 = 17.0260793396018
x2 = -99.2128488432206
x3 = -20.1676719931916
x4 = 61.513737000143
x5 = -70.9385149609124
x6 = -4.96506923552677
x7 = -48.9473663857839
x8 = -57.8667838362691
x9 = 55.2305516929635
x10 = -1371.0525130368
x11 = -52.0889590393737
x12 = -23.8146251570655
x13 = 76.7163397578079
x14 = 96.0712561896308
x15 = 42.1588205683201
x16 = -532.247274528328
x17 = -32.7340426075507
x18 = 23.8146251570655
x19 = -89.7880708824512
x20 = 99.2128488432206
x21 = 13.884486686012
x22 = -4.45970872524261
x23 = 61.0083764898589
x24 = -17.5314398498859
x25 = -39.5225884250145
x26 = 48.4420058754997
x27 = 58.3721443465533
x28 = 67.7969223073226
x29 = -86.1411177185772
x30 = -1.82347658193698
x31 = 4.45970872524261
x32 = 92.4243030257568
x33 = -96.0712561896308
x34 = 10.7428940324222
x35 = 33.2394031178349
x36 = 82.9995250649874
x37 = -30.0978104642451
x38 = -55.2305516929635
x39 = 26.4508573003712
x40 = 83.5048855752716
x41 = -170.964119365502
x42 = 52.0889590393737
x43 = -42.1588205683201
x44 = -61.513737000143
x45 = 1.82347658193698
x46 = -76.7163397578079
x47 = 77.221700268092
x48 = 45.8057737321941
x49 = -48.4420058754997
x50 = -92.929663536041
x51 = 42.6641810786043
x52 = -33.2394031178349
x53 = -64.1499691434487
x54 = 11.2482545427064
x55 = 32.7340426075507
x56 = 74.0801076145022
x57 = -79.8579324113977
x58 = -26.9562178106553
x59 = -35.8756352611405
x60 = 86.6464782288614
x61 = 39.5225884250145
x62 = 8.10666188911656
x63 = 17.5314398498859
x64 = -83.5048855752716
x65 = 70.4331544506283
x66 = -10.7428940324222
x67 = 39.0172279147303
x68 = -74.0801076145022
x69 = 89.7880708824512
x70 = 30.0978104642451
x71 = -98.7074883329364
x72 = 48.9473663857839
x73 = -541.672052489097
x74 = -70.4331544506283
x75 = -67.7969223073226
x76 = -92.4243030257568
x77 = 86.1411177185772
x78 = -11.2482545427064
x79 = -77.221700268092
x80 = -8.10666188911656
x81 = 20.1676719931916
x82 = 64.1499691434487
x83 = 80.3632929216818
x84 = 54.7251911826793
x85 = -26.4508573003712
x86 = -54.7251911826793
x87 = -45.8057737321941
x88 = 98.7074883329364
x89 = -13.884486686012
x89 = -13.884486686012