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(x^2)*cos(2*x)=-1 la ecuación

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Solución numérica:

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Solución

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

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

Como D = 0 hay sólo una raíz.
w = -b/2a = -0/2/(2)

$$w_{1} = 0$$
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:
$$x_{1} = \pi n + \operatorname{acos}{\left(w_{1} \right)}$$
$$x_{1} = \pi n + \operatorname{acos}{\left(0 \right)}$$
$$x_{1} = \pi n + \frac{\pi}{2}$$
$$x_{2} = \pi n + \operatorname{acos}{\left(w_{1} \right)} - \pi$$
$$x_{2} = \pi n - \pi + \operatorname{acos}{\left(0 \right)}$$
$$x_{2} = \pi n - \frac{\pi}{2}$$
Gráfica
Respuesta numérica [src]
x1 = 11.7773676831271
x2 = 60.4757952936653
x3 = -18.0626252282917
x4 = 32.2018068797359
x5 = 40.0549946907729
x6 = -10.2149679677613
x7 = 49.4798800672358
x8 = -85.6084680342239
x9 = 54.1926435252939
x10 = -80.895934425846
x11 = 85.6084680342239
x12 = 52.6214963784489
x13 = -84.0375326851308
x14 = 51.0510724701588
x15 = -33.7716826320301
x16 = -41.6263912176569
x17 = 2.2574379712713
x18 = -62.0463250297136
x19 = -35.3433176250807
x20 = 27.4882739974971
x21 = 1.18320719655542
x22 = 55.763108804917
x23 = 19.636250826255
x24 = 77.7543354734398
x25 = -2.2574379712713
x26 = -46.338258782752
x27 = 41.6263912176569
x28 = -49.4798800672358
x29 = -24.3464995418853
x30 = -13.3545723535998
x31 = 63.6173747783009
x32 = -71.4711349858573
x33 = 47.9095058017307
x34 = -27.4882739974971
x35 = -77.7543354734398
x36 = 16.4951990519887
x37 = 30.6299954350716
x38 = 66.7589560779529
x39 = -63.6173747783009
x40 = 69.9005388737833
x41 = 24.3464995418853
x42 = 74.6127357087493
x43 = -76.1837079976702
x44 = 98.1748223010723
x45 = -82.4668806776415
x46 = 91.8916443306234
x47 = -25.9188836742249
x48 = 5.48114120661372
x49 = 84.0375326851308
x50 = -57.3342180325701
x51 = -16.4951990519887
x52 = -99.7455164960176
x53 = 71.4711349858573
x54 = 46.338258782752
x55 = -69.9005388737833
x56 = 18.0626252282917
x57 = -93.4623242046619
x58 = -91.8916443306234
x59 = 76.1837079976702
x60 = 68.3295331245467
x61 = -38.4848475971914
x62 = -7.07856296729616
x63 = 38.4848475971914
x64 = 99.7455164960176
x65 = 8.63267025757037
x66 = -54.1926435252939
x67 = 82.4668806776415
x68 = -68.3295331245467
x69 = 3.95891449098817
x70 = -60.4757952936653
x71 = -3.95891449098817
x72 = 25.9188836742249
x73 = -5.48114120661372
x74 = 33.7716826320301
x75 = -55.763108804917
x76 = 62.0463250297136
x77 = 96.6039205206259
x78 = -32.2018068797359
x79 = 90.3207274999261
x80 = -11.7773676831271
x81 = -40.0549946907729
x82 = -19.636250826255
x83 = -90.3207274999261
x84 = 10.2149679677613
x85 = -98.1748223010723
x86 = 88.7500559433002
x87 = -47.9095058017307
x88 = -79.3252939627883
x88 = -79.3252939627883