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cos^2x-sin^2x+cosx=0 la ecuación

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Solución numérica:

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Solución

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

(1)^2 - 4 * (2) * (-1) = 9

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

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

o
$$w_{1} = \frac{1}{2}$$
$$w_{2} = -1$$
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:
$$x_{1} = \pi n + \operatorname{acos}{\left(w_{1} \right)}$$
$$x_{1} = \pi n + \operatorname{acos}{\left(\frac{1}{2} \right)}$$
$$x_{1} = \pi n + \frac{\pi}{3}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(w_{2} \right)}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(-1 \right)}$$
$$x_{2} = \pi n + \pi$$
$$x_{3} = \pi n + \operatorname{acos}{\left(w_{1} \right)} - \pi$$
$$x_{3} = \pi n - \pi + \operatorname{acos}{\left(\frac{1}{2} \right)}$$
$$x_{3} = \pi n - \frac{2 \pi}{3}$$
$$x_{4} = \pi n + \operatorname{acos}{\left(w_{2} \right)} - \pi$$
$$x_{4} = \pi n - \pi + \operatorname{acos}{\left(-1 \right)}$$
$$x_{4} = \pi n$$
Gráfica
Respuesta rápida [src]
     -pi 
x1 = ----
      3  
$$x_{1} = - \frac{\pi}{3}$$
     pi
x2 = --
     3 
$$x_{2} = \frac{\pi}{3}$$
x2 = pi/3
Suma y producto de raíces [src]
suma
  pi   pi
- -- + --
  3    3 
$$- \frac{\pi}{3} + \frac{\pi}{3}$$
=
0
$$0$$
producto
-pi  pi
----*--
 3   3 
$$- \frac{\pi}{3} \frac{\pi}{3}$$
=
   2 
-pi  
-----
  9  
$$- \frac{\pi^{2}}{9}$$
-pi^2/9
Respuesta numérica [src]
x1 = 38.7463093942741
x2 = 40.8407042778045
x3 = -24.0855436775217
x4 = -51.3126800086333
x5 = 32.4631240870945
x6 = -59.690260457585
x7 = -57.5958653158129
x8 = 91.1061868116125
x9 = -32.4631240870945
x10 = -74.3510261349584
x11 = 76.4454212373516
x12 = 47.1238897752019
x13 = -40.8407044009017
x14 = 3.14159271706432
x15 = -47.1238900222279
x16 = 3.14159267447126
x17 = 9.42477818680547
x18 = -95.2949771588904
x19 = 28.2743338652086
x20 = 34.5575190335478
x21 = 91.1061863890352
x22 = -21.9911485864549
x23 = -76.4454212373516
x24 = -53.4070752795041
x25 = -30.3687289847013
x26 = -7.33038285837618
x27 = 91.1061869261407
x28 = 65.9734457528689
x29 = -40.8407044128941
x30 = 80.634211442138
x31 = -84.8230015251551
x32 = 78.5398161904624
x33 = 55.5014702134197
x34 = -99.4837673636768
x35 = -78.5398161151012
x36 = -47.1238905036874
x37 = -13.6135681655558
x38 = -49.2182849062401
x39 = 84.8230014287926
x40 = 19.8967534727354
x41 = 107.86134777325
x42 = -34.5575189638817
x43 = 82.7286065445312
x44 = -40.8407047547408
x45 = 72.2566310277195
x46 = 63.8790506229925
x47 = 68.0678408277789
x48 = 74.3510261349584
x49 = -84.8230022421807
x50 = 53.4070753369186
x51 = 57.5958653158129
x52 = -3.14159287255706
x53 = -91.1061871711313
x54 = -61.7846555205993
x55 = -719.424718069224
x56 = -11.5191730631626
x57 = 21.9911485851931
x58 = 47.1238901206303
x59 = 26.1799387799149
x60 = 59.6902605931502
x61 = -93.2005820564972
x62 = -72.256630877064
x63 = -19.8967534727354
x64 = -68.0678408277789
x65 = -65.9734457650482
x66 = -70.162235930172
x67 = 36.6519142918809
x68 = 15.7079634367135
x69 = -15.7079632965016
x70 = 3.14159276530697
x71 = 99.4837673636768
x72 = -9.42477812311019
x73 = 47.1238894268221
x74 = 70.162235930172
x75 = -17.8023583703422
x76 = -646.120889088301
x77 = -5.23598775598299
x78 = 13.6135681655558
x79 = -55.5014702134197
x80 = -28.2743337200245
x81 = 24.0855436775217
x82 = -84.8230014829768
x83 = 11.5191730631626
x84 = -40.8407049942712
x85 = -63.8790506229925
x86 = 97.389372486408
x87 = 3.14159322994749
x88 = -97.3893724356252
x89 = 47.1238898268985
x90 = 21.9911485973609
x91 = 61.7846555205993
x92 = 17.8023583703422
x93 = -26.1799387799149
x94 = 91.1061868861836
x95 = 30.3687289847013
x95 = 30.3687289847013