Use De Moivre's theorem to write the complex number in trigonometric form: (cos(3pi/12) + i sin (3pi/12))^5

A) cos(15 pi/12) + isin (15pi/12)
B) 5(cos(3 pi/12) + isin (3 pi/12)
C) Cos (3pi/60) + isin (3pi/60)
D) Cos (3pi/12)^5+i sin (3pi/12)^5

Respuesta :

[tex]\boxed{\text{De Moivre's Theorem: } (cos\theta + isin\theta )^{n} = cosn\theta + isin(n\theta )}[/tex]

[tex](cos\frac{3\pi}{12} + isin\frac{3\pi}{12})^{5} = cos\frac{5 \cdot 3\pi}{12} + isin\frac{5 \cdot 3\pi}{12}[/tex]
[tex] = cos\frac{15\pi}{12} + isin\frac{15\pi}{12} \text{ or (A)}[/tex]


(cos (3π/12) + i sin (3π/12))⁵ = (cos (15π/12) + i sin (15π/12))

Further explanation

There are many types of numbers in mathematics such as :

  • Natural Numbers : 1 , 2 , 3 , 4 , 5 , . . .
  • Whole Numbers : 0 , 1 , 2 , 3 , 5 , . . .
  • Integers : . . . , - 3 , - 2 , - 1 , 0 , 1 , 2 , 3 , 4 , . . .
  • etc

Complex Number consist of Real Number and Imaginary Number and can be expressed as :

[tex]Z = a + b ~ i[/tex]

The absolute value of complex number is also called Modulus and can be calculated using this formula :

[tex]|Z| = \sqrt { a^2 + b^2 }[/tex]

Let us tackle the problem.

De Moivre's formula for complex numbers is as follows :

[tex]\large {\boxed {[r( \cos \theta + i\sin \theta)]^n = r^n(\cos n\theta + i\sin n\theta)} }[/tex]

Using the formula above, we can solve the problem in the following way

[tex][\cos (\frac{3 \pi}{12}) + i\sin (\frac{3 \pi}{12})]^5 = \cos (5 \times \frac{3 \pi}{12}) + i\sin (5 \times \frac{3 \pi}{12})[/tex]

[tex]\large {\boxed {[\cos (\frac{3 \pi}{12}) + i\sin (\frac{3 \pi}{12})]^5 = \cos (\frac{15 \pi}{12}) + i\sin (\frac{15 \pi}{12})}}[/tex]

Learn more

  • Complex Numbers : https://brainly.com/question/5056377
  • Match Each Product of Complex Numbers : https://brainly.com/question/1514840
  • Graph of The Complex Plane : https://brainly.com/question/10662770

Answer details

Grade: High School

Subject: Mathematics

Chapter: Complex Numbers

Keywords: Complex , Number , Real , Imaginary , Whole , Natural , Integers

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