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4cos^4(x)-1=0

Solución

4 cos^{4} (x) - 1 = 0

Solución

x = 0.78539 \dots + 2 πn, x = 2 π - 0.78539 \dots + 2 πn, x = 2.35619 \dots + 2 πn, x = - 2.35619 \dots + 2 πn

Grados

x = 4 5^{\circ} + 36 0^{\circ} n, x = 31 5^{\circ} + 36 0^{\circ} n, x = 13 5^{\circ} + 36 0^{\circ} n, x = - 13 5^{\circ} + 36 0^{\circ} n

Pasos de solución

4 cos^{4} (x) - 1 = 0

Usando el método de sustitución

4 cos^{4} (x) - 1 = 0

Sea:

cos (x) = u

4 u^{4} - 1 = 0

4 u^{4} - 1 = 0 : u = \frac{1}{2}, u = - \frac{1}{2}, u = i \frac{1}{2}, u = - i \frac{1}{2}

4 u^{4} - 1 = 0

Mover

1

al lado derecho

4 u^{4} - 1 = 0

Sumar

1

a ambos lados

4 u^{4} - 1 + 1 = 0 + 1

Simplificar

4 u^{4} = 1

4 u^{4} = 1

Dividir ambos lados entre

4

4 u^{4} = 1

Dividir ambos lados entre

4

\frac{4 u ^{4}}{4} = \frac{1}{4}

Simplificar

u^{4} = \frac{1}{4}

u^{4} = \frac{1}{4}

Re-escribir la ecuación con

v = u^{2}

v^{2} = u^{4}

v^{2} = \frac{1}{4}

Resolver

v^{2} = \frac{1}{4} : v = \frac{1}{4}, v = - \frac{1}{4}

v^{2} = \frac{1}{4}

Para

(g (x))^{2} = f (a)

las soluciones son

g (x) = f (a), - f (a)

v = \frac{1}{4}, v = - \frac{1}{4}

v = \frac{1}{4}, v = - \frac{1}{4}

Sustituir hacia atrás la

v = u^{2},

resolver para

u

Resolver

u^{2} = \frac{1}{4} : u = \frac{1}{2}, u = - \frac{1}{2}

u^{2} = \frac{1}{4}

Simplificar

\frac{1}{4} : \frac{1}{2}

\frac{1}{4}

Aplicar la siguiente propiedad de los radicales:

asumiendo que

a \geq 0, b \geq 0

= \frac{1}{4}

4 = 2

4

Descomponer el número en factores primos:

4 = 2^{2}

= 2^{2}

Aplicar las leyes de los exponentes:

2^{2} = 2

= 2

= \frac{1}{2}

Aplicar la regla

1 = 1

= \frac{1}{2}

Para

x^{2} = f (a)

las soluciones son

x = f (a), - f (a)

u = \frac{1}{2}, u = - \frac{1}{2}

Resolver

u^{2} = - \frac{1}{4} : u = i \frac{1}{2}, u = - i \frac{1}{2}

u^{2} = - \frac{1}{4}

Simplificar

- \frac{1}{4} : - \frac{1}{2}

- \frac{1}{4}

Simplificar

\frac{1}{4} : \frac{1}{2}

\frac{1}{4}

Aplicar la siguiente propiedad de los radicales:

asumiendo que

a \geq 0, b \geq 0

= \frac{1}{4}

4 = 2

4

Descomponer el número en factores primos:

4 = 2^{2}

= 2^{2}

Aplicar las leyes de los exponentes:

2^{2} = 2

= 2

= \frac{1}{2}

= - \frac{1}{2}

Aplicar la regla

1 = 1

= - \frac{1}{2}

Para

x^{2} = f (a)

las soluciones son

x = f (a), - f (a)

u = - \frac{1}{2}, u = - - \frac{1}{2}

Simplificar

- \frac{1}{2} : i \frac{1}{2}

- \frac{1}{2}

Aplicar las leyes de los exponentes:

- a = - 1 a

- \frac{1}{2} = - 1 \frac{1}{2}

= - 1 \frac{1}{2}

Aplicar las propiedades de los numeros imaginarios:

- 1 = i

= i \frac{1}{2}

Simplificar

- - \frac{1}{2} : - i \frac{1}{2}

- - \frac{1}{2}

Simplificar

- \frac{1}{2} : i \frac{1}{2}

- \frac{1}{2}

Aplicar las leyes de los exponentes:

- a = - 1 a

- \frac{1}{2} = - 1 \frac{1}{2}

= - 1 \frac{1}{2}

Aplicar las propiedades de los numeros imaginarios:

- 1 = i

= i \frac{1}{2}

= - i \frac{1}{2}

u = i \frac{1}{2}, u = - i \frac{1}{2}

Las soluciones son

u = \frac{1}{2}, u = - \frac{1}{2}, u = i \frac{1}{2}, u = - i \frac{1}{2}

Sustituir en la ecuación

u = cos (x)

cos (x) = \frac{1}{2}, cos (x) = - \frac{1}{2}, cos (x) = i \frac{1}{2}, cos (x) = - i \frac{1}{2}

cos (x) = \frac{1}{2}, cos (x) = - \frac{1}{2}, cos (x) = i \frac{1}{2}, cos (x) = - i \frac{1}{2}

cos (x) = \frac{1}{2} : x = arccos (\frac{1}{2}) + 2 πn, x = 2 π - arccos (\frac{1}{2}) + 2 πn

cos (x) = \frac{1}{2}

Aplicar propiedades trigonométricas inversas

cos (x) = \frac{1}{2}

Soluciones generales para

cos (x) = \frac{1}{2}

cos (x) = a \Rightarrow x = arccos (a) + 2 πn, x = 2 π - arccos (a) + 2 πn

x = arccos (\frac{1}{2}) + 2 πn, x = 2 π - arccos (\frac{1}{2}) + 2 πn

x = arccos (\frac{1}{2}) + 2 πn, x = 2 π - arccos (\frac{1}{2}) + 2 πn

cos (x) = - \frac{1}{2} : x = arccos (- \frac{1}{2}) + 2 πn, x = - arccos (- \frac{1}{2}) + 2 πn

cos (x) = - \frac{1}{2}

Aplicar propiedades trigonométricas inversas

cos (x) = - \frac{1}{2}

Soluciones generales para

cos (x) = - \frac{1}{2}

cos (x) = - a \Rightarrow x = arccos (- a) + 2 πn, x = - arccos (- a) + 2 πn

x = arccos (- \frac{1}{2}) + 2 πn, x = - arccos (- \frac{1}{2}) + 2 πn

x = arccos (- \frac{1}{2}) + 2 πn, x = - arccos (- \frac{1}{2}) + 2 πn

cos (x) = i \frac{1}{2} :

Sin solución

cos (x) = i \frac{1}{2}

Sin soluci \overset{o}{ˊ} n

cos (x) = - i \frac{1}{2} :

Sin solución

cos (x) = - i \frac{1}{2}

Sin soluci \overset{o}{ˊ} n

Combinar toda las soluciones

x = arccos (\frac{1}{2}) + 2 πn, x = 2 π - arccos (\frac{1}{2}) + 2 πn, x = arccos (- \frac{1}{2}) + 2 πn, x = - arccos (- \frac{1}{2}) + 2 πn

Mostrar soluciones en forma decimal

x = 0.78539 \dots + 2 πn, x = 2 π - 0.78539 \dots + 2 πn, x = 2.35619 \dots + 2 πn, x = - 2.35619 \dots + 2 πn

Ejemplos populares

arccos(2x)-arccos(x)= pi/3

arccos (2 x) - arccos (x) = \frac{π}{3}

cos(2θ)= 1/2 ,0<= θ<= 2pi

cos (2 θ) = \frac{1}{2}, 0 \leq θ \leq 2 π

tan(x-pi/2)=(sqrt(3))/3

tan (x - \frac{π}{2}) = \frac{3}{3}

2=2cos(3x)

2 = 2 cos (3 x)

cos(x)=((7^2+10^2-6^2)/(2(10)(6)))

cos (x) = (\frac{7 ^{2} + 1 0 ^{2} - 6 ^{2}}{2 ( 10 ) ( 6 )})