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Ch. 8 - Techniques of Integration
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 8, Problema 8.4.58

Area: Find the area enclosed by the ellipse x²/a² + y²/b² = 1.

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1
Recognize that the ellipse is given by the equation \(\frac{x^{2}}{a^{2}} + \frac{y^{2}}{b^{2}} = 1\), where \(a\) and \(b\) are the semi-major and semi-minor axes respectively.
Express \(y\) in terms of \(x\) by solving the ellipse equation for \(y\): \(y = \pm b \sqrt{1 - \frac{x^{2}}{a^{2}}}\).
Set up the integral for the area of the ellipse by integrating the positive half of \(y\) from \(-a\) to \(a\) and then doubling the result to account for the negative half: \(\text{Area} = 2 \int_{-a}^{a} b \sqrt{1 - \frac{x^{2}}{a^{2}}} \, dx\).
Use a substitution to simplify the integral, such as \(x = a \sin \theta\), which transforms the integral limits and the integrand into a trigonometric form.
Evaluate the integral using the substitution and then multiply by 2 and \(b\) to find the total area enclosed by the ellipse.

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The ellipse is defined by the equation x²/a² + y²/b² = 1, where 'a' and 'b' are the semi-major and semi-minor axes respectively. This equation describes all points (x, y) that lie on the ellipse, forming a closed curve symmetric about both axes.
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The area enclosed by an ellipse is given by the formula A = πab, where 'a' and 'b' are the lengths of the semi-major and semi-minor axes. This formula is derived by scaling the area of a unit circle by the factors 'a' and 'b' along the x and y axes.
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Calculus can be used to find the area enclosed by curves by integrating the function that defines the boundary. For an ellipse, one can set up an integral using the ellipse equation to find the area, confirming the formula A = πab through definite integration.
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