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Ch. 11 - Parametric Equations and Polar Coordinates
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 11, Problema 11.2.47a

Cycloid


a. Find the length of one arch of the cycloid x = a(t − sin t), y = a(1 − cos t).

Guida verificata passo dopo passo
1
Identify the parametric equations of the cycloid: \(x = a(t - \sin t)\) and \(y = a(1 - \cos t)\), where \(t\) is the parameter.
Recall the formula for the arc length \(L\) of a curve defined parametrically by \(x = x(t)\) and \(y = y(t)\) over an interval \(t \in [\alpha, \beta]\): \(L = \int_{\alpha}^{\beta} \sqrt{\left(\frac{dx}{dt}\right)^2 + \left(\frac{dy}{dt}\right)^2} \, dt\).
Compute the derivatives \(\frac{dx}{dt}\) and \(\frac{dy}{dt}\): \(\frac{dx}{dt} = a(1 - \cos t)\) \(\frac{dy}{dt} = a \sin t\).
Substitute these derivatives into the arc length integral and simplify the integrand: \(L = \int_{0}^{2\pi} \sqrt{a^2(1 - \cos t)^2 + a^2 \sin^2 t} \, dt\) Simplify inside the square root to express the integrand in a simpler form.
Evaluate the integral over one full arch of the cycloid, which corresponds to \(t\) going from \(0\) to \(2\pi\), to find the length of one arch.

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Parametric Equations

Parametric equations express the coordinates of points on a curve as functions of a parameter, often denoted t. For the cycloid, both x and y are given in terms of t, allowing us to analyze the curve's properties by differentiating with respect to t.
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Parameterizing Equations

Arc Length of Parametric Curves

The 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 (dx/dt)^2 + (dy/dt)^2 over that interval. This formula accounts for the combined rate of change in both x and y directions.
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Arc Length of Parametric Curves

Properties of the Cycloid

A cycloid is the path traced by a point on the rim of a rolling circle. One arch corresponds to t going from 0 to 2π. Understanding this interval helps set the limits for integration when calculating the length of one arch.
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Properties of Functions