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Ch. 5 - Complex Numbers, Polar Coordinates and Parametric Equations
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601당신이 사용하는 게 아니라요?교과서 변경
5장, 문제 5.3.54

In Exercises 49–58, convert each rectangular equation to a polar equation that expresses r in terms of θ.


x² + y² = 16

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Recall the relationship between rectangular coordinates (x, y) and polar coordinates (r, \(\theta\)): \(x = r \cos\theta\) and \(y = r \sin\theta\).
Substitute \(x = r \cos\theta\) and \(y = r \sin\theta\) into the given equation \(x^{2} + y^{2} = 16\).
This substitution gives the equation \((r \cos\theta)^{2} + (r \sin\theta)^{2} = 16\).
Simplify the equation by factoring out \(r^{2}\): \(r^{2}(\cos^{2}\theta + \sin^{2}\theta) = 16\).
Use the Pythagorean identity \(\cos^{2}\theta + \sin^{2}\theta = 1\) to simplify to \(r^{2} = 16\), then solve for \(r\) to express it in terms of \(\theta\).

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Rectangular and Polar Coordinate Systems

Rectangular coordinates represent points using (x, y) on a plane, while polar coordinates use (r, θ), where r is the distance from the origin and θ is the angle from the positive x-axis. Understanding how these systems relate is essential for converting equations between them.
추천 영상:
05:32
Intro to Polar Coordinates

Relationship Between Rectangular and Polar Coordinates

The key formulas connecting the two systems are x = r cos θ and y = r sin θ. Additionally, r² = x² + y². These relationships allow substitution of x and y in terms of r and θ to rewrite rectangular equations in polar form.
추천 영상:
06:17
Convert Points from Polar to Rectangular

Converting Equations to Express r in Terms of θ

To convert a rectangular equation to polar form expressing r as a function of θ, substitute x and y with r cos θ and r sin θ, respectively, then solve algebraically for r. This process isolates r, showing how the radius varies with the angle θ.
추천 영상:
6:50
Convert Equations from Polar to Rectangular