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Ch.12 - Parametric and Polar Curves
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Non è quello che usi tu?Cambia libro di testo
Capitolo 12, Problema 12.1.88

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


x = sin t, y = t - cos t; 0 ≤ t ≤ π/2

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Recall the formula for the arc length of a parametric curve given by \(x = x(t)\) and \(y = y(t)\) over the interval \(a \leq t \leq b\): \[L = \int_a^b \sqrt{\left(\frac{dx}{dt}\right)^2 + \left(\frac{dy}{dt}\right)^2} \, dt\]
Identify the given functions: \(x(t) = \sin t\) \(y(t) = t - \cos t\) and the interval: \(0 \leq t \leq \frac{\pi}{2}\)
Compute the derivatives of \(x(t)\) and \(y(t)\) with respect to \(t\): \[\frac{dx}{dt} = \cos t\] \[\frac{dy}{dt} = 1 + \sin t\]
Substitute the derivatives into the arc length formula under the square root: \[\sqrt{(\cos t)^2 + (1 + \sin t)^2} = \sqrt{\cos^2 t + (1 + \sin t)^2}\]
Simplify the expression inside the square root as much as possible before integrating, then set up the integral for the arc length: \[L = \int_0^{\frac{\pi}{2}} \sqrt{\cos^2 t + (1 + \sin t)^2} \, dt\] This integral can then be evaluated to find the arc length.

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Parametric Equations

Parametric equations express the coordinates of points on a curve as functions of a parameter, often denoted t. Here, x and y are given in terms of t, allowing the curve to be analyzed by studying these functions over the specified interval.
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Parameterizing Equations

Arc Length Formula for Parametric Curves

The arc length of a curve defined parametrically by x(t) and y(t) from t = a to t = b is found by integrating the square root of the sum of the squares of the derivatives: ∫ from a to b √[(dx/dt)² + (dy/dt)²] dt. This formula measures the distance along the curve.
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Arc Length of Parametric Curves

Differentiation of Parametric Functions

To apply the arc length formula, one must compute the derivatives dx/dt and dy/dt accurately. Differentiation rules for trigonometric and polynomial functions are used here to find these derivatives, which are essential for evaluating the integral.
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Differentiation of Parametric Curves
Pratica correlata
Domanda del libro di testo

31–38. Equations of parabolas Find an equation of the following parabolas. Unless otherwise specified, assume the vertex is at the origin.

A parabola that opens to the right with directrix x = -4

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85–87. Grazing goat problems Consider the following sequence of problems related to grazing goats tied to a rope. (See the Guided Project Grazing goat problems.)


A circular corral of unit radius is enclosed by a fence. A goat inside the corral is tied to the fence with a rope of length 0≤a≤2 (see figure). What is the area of the region (inside the corral) that the goat can graze? Check your answer with the special cases a=0 and a=2.


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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 = 8 + 2t, y = 1; −∞ < t < ∞

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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.

Let L be the latus rectum of the parabola y ² =4px for p>0. Let F be the focus of the parabola, P be any point on the parabola to the left of L, and D be the (shortest) distance between P and L. Show that for all P, D+|FP|+ is a constant. Find the constant.

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Given three polar coordinate representations for the origin.

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


r = 1 - sin θ; (1/2, π/6)

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