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Ch.12 - Parametric and Polar Curves
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
All textbooksBriggs 3rd EditionCh.12 - Parametric and Polar CurvesProblem 12.R.1a
Chapter 12, Problem 12.R.1a

Explain why or why not Determine whether the following statements are true and give an explanation or counterexample.
a. A set of parametric equations for a given curve is always unique.

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Understand the meaning of parametric equations: Parametric equations express the coordinates of points on a curve as functions of a parameter, usually denoted as \(t\). For example, \(x = f(t)\) and \(y = g(t)\) describe a curve in the plane.
Consider the uniqueness of parametric representations: Ask yourself if there can be more than one way to describe the same curve using different parametric equations. Think about how changing the parameter or reparametrizing the curve might affect the equations.
Recall that a curve can be reparametrized: If you have one set of parametric equations \(x = f(t)\) and \(y = g(t)\), you can often create another set by substituting \(t\) with a different parameter function \(s = h(t)\), where \(h\) is a one-to-one function. This produces a different parametric form for the same curve.
Conclude about uniqueness: Since multiple parameterizations can describe the same curve, the set of parametric equations for a given curve is generally not unique.
Provide a counterexample: For instance, the circle \(x = \cos t\), \(y = \sin t\) can also be described by \(x = \cos(2t)\), \(y = \sin(2t)\), which traces the same circle but at a different speed and parameterization.

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Key Concepts

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

Parametric Equations

Parametric equations represent a curve by expressing the coordinates as functions of a parameter, usually denoted as t. They allow the description of curves that may not be functions in the traditional y = f(x) form, providing flexibility in representing complex paths.
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Uniqueness of Parametric Representations

A single curve can have multiple parametric representations because different parameterizations can trace the same set of points in various ways. This means parametric equations for a curve are generally not unique, as reparameterizations or different functional forms can describe the same curve.
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Counterexamples in Mathematics

A counterexample is a specific case that disproves a general statement or claim. To show that parametric equations are not always unique, one can provide two distinct parametric forms that generate the same curve, demonstrating the statement is false.
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Related Practice
Textbook Question

44–49. Areas of regions Find the area of the following regions.

The region inside the limaçon r=2+cosθ and outside the circle r=2

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Textbook Question

51–52. {Use of Tech} Arc length of polar curves Find the approximate length of the following curves.

The limaçon r=3−6cosθ

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Textbook Question

A polar conic section Consider the equation r² = sec2θ

b. Find the vertices, foci, directrices, and eccentricity of the curve."

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Textbook Question

Explain why or why not Determine whether the following statements are true and give an explanation or counterexample.

c. The polar coordinates (3, -3π/4) and (-3, π/4) describe the same point in the plane.

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Textbook Question

53–57. Conic sections

a. Determine whether the following equations describe a parabola, an ellipse, or a hyperbola.

x²/4 + y²/25 = 1

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Textbook Question

22–23. Arc length Find the length of the following curves.

x = cos 2t, y = 2t - sin 2t; 0 ≤ t ≤ π/4

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