Ch. 5 - Complex Numbers, Polar Coordinates and Parametric Equations

Blitzer3rd EditionTrigonometryISBN: 9780137316601Not the one you use?Change textbook

Blitzer 3rd Edition

Ch. 5 - Complex Numbers, Polar Coordinates and Parametric Equations

Problem 7

Chapter 5, Problem 7

Perform the indicated operation. Leave answers in polar form. [2(cos 10° + i sin 10°)]⁵

Verified step by step guidance

Recognize that the expression is in polar form, where the complex number is given by \(r(\cos \theta + i \sin \theta)\) with \(r = 2\) and \(\theta = 10^\circ\).

Recall De Moivre's Theorem, which states that for a complex number in polar form, raising it to the power \(n\) results in \(r^n \left( \cos(n\theta) + i \sin(n\theta) \right)\).

Apply De Moivre's Theorem to the given expression: raise the magnitude to the fifth power, \(r^5 = 2^5\), and multiply the angle by 5, \(5 \times 10^\circ\).

Write the resulting expression as \(2^5 \left( \cos(50^\circ) + i \sin(50^\circ) \right)\), which is the polar form of the complex number raised to the fifth power.

Leave the answer in this polar form without converting to rectangular form or calculating the numerical values.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Polar Form of Complex Numbers

A complex number can be expressed in polar form as r(cos θ + i sin θ), where r is the magnitude and θ is the argument (angle). This form is useful for multiplication and exponentiation because it separates the magnitude and angle, simplifying calculations involving powers and roots.

De Moivre's Theorem

De Moivre's Theorem states that for a complex number in polar form, raising it to the nth power results in r^n [cos(nθ) + i sin(nθ)]. This theorem allows easy computation of powers of complex numbers by raising the magnitude to the power and multiplying the angle by n.

Exponentiation of Complex Numbers in Polar Form

To raise a complex number in polar form to a power, apply De Moivre's Theorem by raising the modulus to the power and multiplying the argument by the exponent. This process yields the result in polar form, which is often preferred for clarity and further operations.

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