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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 7, Problema 7.6.65

Evaluate the integrals in Exercises 53–76.
65. ∫3dr/√(1-4(r-1)²)

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Recognize that the integral has the form \( \int \frac{3 \, dr}{\sqrt{1 - 4(r-1)^2}} \), which resembles the standard integral \( \int \frac{dx}{\sqrt{a^2 - x^2}} = \arcsin\left(\frac{x}{a}\right) + C \).
Make a substitution to simplify the expression inside the square root. Let \( u = r - 1 \), so that \( du = dr \). The integral becomes \( \int \frac{3 \, du}{\sqrt{1 - 4u^2}} \).
Rewrite the expression under the square root as \( 1 - (2u)^2 \), which suggests another substitution or recognizing \( a = 1 \) and \( x = 2u \).
To match the standard form, factor out the constant inside the square root: \( \sqrt{1 - 4u^2} = \sqrt{1 - (2u)^2} \). Consider substituting \( w = 2u \), so \( dw = 2 du \) or \( du = \frac{dw}{2} \).
Rewrite the integral in terms of \( w \) and use the standard arcsine integral formula: \( \int \frac{dw}{\sqrt{1 - w^2}} = \arcsin(w) + C \). After integrating, substitute back \( w = 2u \) and \( u = r - 1 \) to express the answer in terms of \( r \).

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