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Ch.12 - Parametric and Polar Curves
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243당신이 사용하는 게 아니라요?교과서 변경
12장, 문제 12.1.54

53–56. Circular motion Find parametric equations that describe the circular path of the following objects. For Exercises 53–55, assume (x, y) denotes the position of the object relative to the origin at the center of the circle. Use the units of time specified in the problem. There are many ways to describe any circle.


The tip of the 15-inch second hand of a clock completes one revolution in 60 seconds.

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1
Identify the radius of the circular path, which is the length of the second hand. Here, the radius \(r\) is 15 inches.
Determine the angular velocity \(\omega\) of the second hand. Since it completes one full revolution (which is \(2\pi\) radians) in 60 seconds, calculate \(\omega\) as \(\omega = \frac{2\pi}{60}\) radians per second.
Set up the parametric equations for the circular motion. The general form for a circle centered at the origin is \(x(t) = r \cos(\omega t)\) and \(y(t) = r \sin(\omega t)\), where \(t\) is time in seconds.
Substitute the known values of \(r\) and \(\omega\) into the parametric equations to express \(x(t)\) and \(y(t)\) explicitly in terms of \(t\).
Interpret the parametric equations: as \(t\) increases from 0 to 60, the point \((x(t), y(t))\) traces the circular path of the second hand exactly once.

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주요 개념

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Parametric Equations for Circular Motion

Parametric equations express the coordinates of a point on a circle as functions of time, typically using sine and cosine functions. For a circle centered at the origin with radius r, the position (x, y) can be described as x = r cos(θ(t)) and y = r sin(θ(t)), where θ(t) is the angle as a function of time.
추천 영상:
가이드 코스
08:02
Parameterizing Equations

Angular Velocity and Period

Angular velocity (ω) measures how fast an object rotates, defined as the angle covered per unit time. It relates to the period (T), the time for one full revolution, by ω = 2π / T. For the clock's second hand, completing one revolution in 60 seconds means ω = 2π / 60 radians per second.
추천 영상:
06:29
Derivatives Applied To Velocity

Relationship Between Linear and Angular Quantities

The linear position on the circle depends on the radius and the angular position. The radius is the length from the center to the point (here, 15 inches), and the angular position changes over time according to angular velocity. This relationship allows converting rotational motion into x and y coordinates.
추천 영상:
07:17
Linearization
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교과서 질문

11–20. Slopes of tangent lines Find the slope of the line tangent to the following polar curves at the given points.


r = 4 cos 2θ; at the tips of the leaves

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교과서 질문

13–30. Graphing conic sections Determine whether the following equations describe a parabola, an ellipse, or a hyperbola, and then sketch a graph of the curve. For each parabola, specify the location of the focus and the equation of the directrix; for each ellipse, label the coordinates of the vertices and foci, and find the lengths of the major and minor axes; for each hyperbola, label the coordinates of the vertices and foci, and find the equations of the asymptotes.


4x = -y²

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교과서 질문

Circles in general Show that the polar equation

r² - 2r r₀ cos(θ - θ₀) = R² - r₀²

describes a circle of radius R whose center has polar coordinates (r₀, θ₀)

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90–94. Focal chords A focal chord of a conic section is a line through a focus joining two points of the curve. The latus rectum is the focal chord perpendicular to the major axis of the conic. Prove the following properties.

The length of the latus rectum of the parabola y ² =4px or x ² =4py is 4|p|.

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교과서 질문

37–52. Curves to parametric equations Find parametric equations for the following curves. Include an interval for the parameter values. Answers are not unique.


The line that passes through the points P(1, 1) and Q(3, 5), oriented in the direction of increasing x

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교과서 질문

81–88. Arc length Find the arc length of the following curves on the given interval.


x = eᵗ sin t, y = eᵗ cos t; 0 ≤ t ≤ 2π

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