Tangent line at the origin Find the polar equation of the line tangent to the polar curve r=4cosθ at the origin. Explain why the slope of this line is undefined.
Ch.12 - Parametric and Polar Curves
12장, 문제 12.1.25
15–30. Working with parametric equations Consider the following parametric equations.
a. Eliminate the parameter to obtain an equation in x and y.
b. Describe the curve and indicate the positive orientation.
x = r − 1, y = r³; −4 ≤ r ≤ 4
검증된 단계별 안내1
Identify the given parametric equations: \(x = r - 1\) and \(y = r^{3}\), with the parameter \(r\) ranging from \(-4\) to \(4\).
To eliminate the parameter \(r\), solve the first equation for \(r\): \(r = x + 1\).
Substitute \(r = x + 1\) into the second equation to express \(y\) solely in terms of \(x\): \(y = (x + 1)^{3}\).
Recognize that the resulting equation \(y = (x + 1)^{3}\) represents a cubic curve, which is a shifted cubic function along the x-axis.
For the positive orientation, note that as \(r\) increases from \(-4\) to \(4\), \(x\) increases from \(-5\) to \(3\), and \(y\) follows the cubic relationship accordingly, indicating the direction of the curve from left to right.

비슷한 문제에 대한 검증된 영상 답변:
이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
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주요 개념
질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.
Parametric Equations
Parametric equations express the coordinates of points on a curve as functions of a parameter, often denoted as t or r. Instead of y as a function of x, both x and y depend on the parameter, allowing representation of more complex curves and motions.
추천 영상:
가이드 코스
Parameterizing Equations
Eliminating the Parameter
Eliminating the parameter involves rewriting the parametric equations to form a single equation relating x and y directly. This is done by solving one equation for the parameter and substituting into the other, which helps in identifying the curve's shape in the xy-plane.
추천 영상:
가이드 코스
Eliminating the Parameter
Curve Orientation and Description
Curve orientation refers to the direction in which the curve is traced as the parameter increases. Describing the curve involves identifying its shape and key features, while orientation indicates the path's direction, important for understanding motion or flow along the curve.
추천 영상:
Summary of Curve Sketching
관련 실천
교과서 질문
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교과서 질문
What is the polar equation of the horizontal line y = 5?
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Tangent lines for a hyperbola Find an equation of the line tangent to the hyperbola x²/a² + y²/b² = 1 at the point (x₀, y₀)
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교과서 질문
33–40. Areas of regions Make a sketch of the region and its bounding curves. Find the area of the region.
The region inside the curve r = √(cos θ)
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교과서 질문
Spiral arc length Consider the spiral r=4θ, for θ≥0.
a. Use a trigonometric substitution to find the length of the spiral, for 0≤θ≤√8.
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