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Popular >

verificar cos(3t)=4cos^3(t)-3cos(t)

Solución

verificar

cos (3 t) = 4 cos^{3} (t) - 3 cos (t)

Solución

Verdadero

Pasos de solución

cos (3 t) = 4 cos^{3} (t) - 3 cos (t)

Manipular el lado derecho

cos (3 t)

Re-escribir usando identidades trigonométricas

cos (3 t)

Reescribir como

= cos (2 t + t)

Utilizar la identidad de suma de ángulos:

cos (s + t) = cos (s) cos (t) - sin (s) sin (t)

= cos (2 t) cos (t) - sin (2 t) sin (t)

Utilizar la identidad trigonométrica del ángulo doble:

sin (2 t) = 2 sin (t) cos (t)

= cos (2 t) cos (t) - 2 sin (t) cos (t) sin (t)

Simplificar

cos (2 t) cos (t) - 2 sin (t) cos (t) sin (t) : cos (t) cos (2 t) - 2 sin^{2} (t) cos (t)

cos (2 t) cos (t) - 2 sin (t) cos (t) sin (t)

2 sin (t) cos (t) sin (t) = 2 sin^{2} (t) cos (t)

2 sin (t) cos (t) sin (t)

Aplicar las leyes de los exponentes:

a^{b} \cdot a^{c} = a^{b + c}

sin (t) sin (t) = sin^{1 + 1} (t)

= 2 cos (t) sin^{1 + 1} (t)

Sumar:

1 + 1 = 2

= 2 cos (t) sin^{2} (t)

= cos (t) cos (2 t) - 2 sin^{2} (t) cos (t)

= cos (t) cos (2 t) - 2 sin^{2} (t) cos (t)

= cos (t) cos (2 t) - 2 sin^{2} (t) cos (t)

Utilizar la identidad trigonométrica del ángulo doble:

cos (2 t) = 2 cos^{2} (t) - 1

= (2 cos^{2} (t) - 1) cos (t) - 2 sin^{2} (t) cos (t)

Utilizar la identidad pitagórica:

cos^{2} (t) + sin^{2} (t) = 1

sin^{2} (t) = 1 - cos^{2} (t)

= (2 cos^{2} (t) - 1) cos (t) - 2 (1 - cos^{2} (t)) cos (t)

Expandir

(2 cos^{2} (t) - 1) cos (t) - 2 (1 - cos^{2} (t)) cos (t) : 4 cos^{3} (t) - 3 cos (t)

(2 cos^{2} (t) - 1) cos (t) - 2 (1 - cos^{2} (t)) cos (t)

= cos (t) (2 cos^{2} (t) - 1) - 2 cos (t) (1 - cos^{2} (t))

Expandir

cos (t) (2 cos^{2} (t) - 1) : 2 cos^{3} (t) - cos (t)

cos (t) (2 cos^{2} (t) - 1)

Poner los parentesis utilizando:

a (b - c) = ab - a c

a = cos (t), b = 2 cos^{2} (t), c = 1

= cos (t) 2 cos^{2} (t) - cos (t) 1

= 2 cos^{2} (t) cos (t) - 1 cos (t)

Simplificar

2 cos^{2} (t) cos (t) - 1 \cdot cos (t) : 2 cos^{3} (t) - cos (t)

2 cos^{2} (t) cos (t) - 1 cos (t)

2 cos^{2} (t) cos (t) = 2 cos^{3} (t)

2 cos^{2} (t) cos (t)

Aplicar las leyes de los exponentes:

a^{b} \cdot a^{c} = a^{b + c}

cos^{2} (t) cos (t) = cos^{2 + 1} (t)

= 2 cos^{2 + 1} (t)

Sumar:

2 + 1 = 3

= 2 cos^{3} (t)

1 \cdot cos (t) = cos (t)

1 cos (t)

Multiplicar:

1 \cdot cos (t) = cos (t)

= cos (t)

= 2 cos^{3} (t) - cos (t)

= 2 cos^{3} (t) - cos (t)

= 2 cos^{3} (t) - cos (t) - 2 (1 - cos^{2} (t)) cos (t)

Expandir

- 2 cos (t) (1 - cos^{2} (t)) : - 2 cos (t) + 2 cos^{3} (t)

- 2 cos (t) (1 - cos^{2} (t))

Poner los parentesis utilizando:

a (b - c) = ab - a c

a = - 2 cos (t), b = 1, c = cos^{2} (t)

= - 2 cos (t) 1 - (- 2 cos (t)) cos^{2} (t)

Aplicar las reglas de los signos

- (- a) = a

= - 2 \cdot 1 cos (t) + 2 cos^{2} (t) cos (t)

Simplificar

- 2 \cdot 1 \cdot cos (t) + 2 cos^{2} (t) cos (t) : - 2 cos (t) + 2 cos^{3} (t)

- 2 \cdot 1 cos (t) + 2 cos^{2} (t) cos (t)

2 \cdot 1 \cdot cos (t) = 2 cos (t)

2 \cdot 1 cos (t)

Multiplicar los numeros:

2 \cdot 1 = 2

= 2 cos (t)

2 cos^{2} (t) cos (t) = 2 cos^{3} (t)

2 cos^{2} (t) cos (t)

Aplicar las leyes de los exponentes:

a^{b} \cdot a^{c} = a^{b + c}

cos^{2} (t) cos (t) = cos^{2 + 1} (t)

= 2 cos^{2 + 1} (t)

Sumar:

2 + 1 = 3

= 2 cos^{3} (t)

= - 2 cos (t) + 2 cos^{3} (t)

= - 2 cos (t) + 2 cos^{3} (t)

= 2 cos^{3} (t) - cos (t) - 2 cos (t) + 2 cos^{3} (t)

Simplificar

2 cos^{3} (t) - cos (t) - 2 cos (t) + 2 cos^{3} (t) : 4 cos^{3} (t) - 3 cos (t)

2 cos^{3} (t) - cos (t) - 2 cos (t) + 2 cos^{3} (t)

Agrupar términos semejantes

= 2 cos^{3} (t) + 2 cos^{3} (t) - cos (t) - 2 cos (t)

Sumar elementos similares:

2 cos^{3} (t) + 2 cos^{3} (t) = 4 cos^{3} (t)

= 4 cos^{3} (t) - cos (t) - 2 cos (t)

Sumar elementos similares:

- cos (t) - 2 cos (t) = - 3 cos (t)

= 4 cos^{3} (t) - 3 cos (t)

= 4 cos^{3} (t) - 3 cos (t)

= 4 cos^{3} (t) - 3 cos (t)

Se demostró que ambos lados pueden tomar la misma forma

\Rightarrow Verdadero

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