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(cos(3x))*(cos(3x)) la ecuación

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Solución numérica:

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Solución

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

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

Como D = 0 hay sólo una raíz.
w = -b/2a = -0/2/(1)

$$w_{1} = 0$$
hacemos cambio inverso
$$\cos{\left(3 x \right)} = w$$
Tenemos la ecuación
$$\cos{\left(3 x \right)} = w$$
es la ecuación trigonométrica más simple
Esta ecuación se reorganiza en
$$3 x = \pi n + \operatorname{acos}{\left(w \right)}$$
$$3 x = \pi n + \operatorname{acos}{\left(w \right)} - \pi$$
O
$$3 x = \pi n + \operatorname{acos}{\left(w \right)}$$
$$3 x = \pi n + \operatorname{acos}{\left(w \right)} - \pi$$
, donde n es cualquier número entero
Dividamos ambos miembros de la ecuación obtenida en
$$3$$
sustituimos w:
$$x_{1} = \frac{\pi n}{3} + \frac{\operatorname{acos}{\left(w_{1} \right)}}{3}$$
$$x_{1} = \frac{\pi n}{3} + \frac{\operatorname{acos}{\left(0 \right)}}{3}$$
$$x_{1} = \frac{\pi n}{3} + \frac{\pi}{6}$$
$$x_{2} = \frac{\pi n}{3} + \frac{\operatorname{acos}{\left(w_{1} \right)}}{3} - \frac{\pi}{3}$$
$$x_{2} = \frac{\pi n}{3} - \frac{\pi}{3} + \frac{\operatorname{acos}{\left(0 \right)}}{3}$$
$$x_{2} = \frac{\pi n}{3} - \frac{\pi}{6}$$
Gráfica
Respuesta rápida [src]
     pi
x1 = --
     6 
$$x_{1} = \frac{\pi}{6}$$
     pi
x2 = --
     2 
$$x_{2} = \frac{\pi}{2}$$
x2 = pi/2
Suma y producto de raíces [src]
suma
pi   pi
-- + --
6    2 
$$\frac{\pi}{6} + \frac{\pi}{2}$$
=
2*pi
----
 3  
$$\frac{2 \pi}{3}$$
producto
pi pi
--*--
6  2 
$$\frac{\pi}{6} \frac{\pi}{2}$$
=
  2
pi 
---
 12
$$\frac{\pi^{2}}{12}$$
pi^2/12
Respuesta numérica [src]
x1 = 4.71238901629785
x2 = 18.3259571004719
x3 = -73.8274272823298
x4 = -5.75958652424928
x5 = 86.3937979052498
x6 = 42.4115007524084
x7 = -89.5353906915371
x8 = -25.6563400574942
x9 = 27.7507351416945
x10 = -47.6474886360566
x11 = 73.8274274357866
x12 = 97.9129710990821
x13 = -87.4409953189147
x14 = 56.0250689512033
x15 = 20.4203521766952
x16 = 31.9395253611477
x17 = 78.0162175417499
x18 = 93.7241808065961
x19 = -80.1106125965004
x20 = 0.523598793698386
x21 = 40.3171056798614
x22 = 16.2315620580511
x23 = -16.2315619891784
x24 = -23.5619449729929
x25 = 9.94837678084721
x26 = -34.0339203815254
x27 = 29.8451302859375
x28 = -38.2227105578705
x29 = -43.4586982782211
x30 = 64.4026493286099
x31 = 88.4881930280058
x32 = 82.205007807797
x33 = -53.9306740746488
x34 = -49.7418836877244
x35 = -21.467549748169
x36 = -14.1371668657739
x37 = 51.8362788611105
x38 = -60.2138591280511
x39 = 95.8185760099185
x40 = -69.6386372143248
x41 = -62.3082544993577
x42 = -27.7507351061626
x43 = -40.3171057809134
x44 = -12.0427718000216
x45 = -96.865773562311
x46 = -78.0162175468244
x47 = -51.8362786947358
x48 = 38.2227106407841
x49 = 7.85398171030129
x50 = 5.75958657756439
x51 = -31.9395254607427
x52 = -36.1283154422719
x53 = 71.7330322578684
x54 = 84.2994028394378
x55 = 53.9306739409302
x56 = 62.308254259517
x57 = 100.007366129875
x58 = 22.51474734437
x59 = 38.2227104061931
x60 = -9.94837684644357
x61 = 14.1371669873783
x62 = 219.387886624637
x63 = -96.8657733416992
x64 = -3.6651914786486
x65 = 34.0339203573462
x66 = -45.5530935467806
x67 = -218.340689710019
x68 = -65.4498467952353
x69 = 60.2138592240082
x70 = -67.5442421196901
x71 = -29.8451301070482
x72 = 44.5058959013899
x73 = -7.85398152418181
x74 = -84.2994030191035
x75 = -82.2050076993983
x76 = 49.7418837022546
x77 = -93.7241808498957
x78 = 75.9218225202323
x79 = -58.1194640191823
x80 = -71.7330322689618
x81 = -95.8185758690479
x82 = -56.0250689637531
x83 = -1.57079639846571
x84 = -91.6297857922845
x85 = 12.0427717588149
x86 = -100.007366130902
x87 = 66.4970444630068
x87 = 66.4970444630068