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Ch. 8 - Integration Techniques
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Non è quello che usi tu?Cambia libro di testo
Capitolo 8, Problema 8.5.54

23-64. Integration Evaluate the following integrals.
54. ∫ (z + 1)/[z(z² + 4)] dz

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Start by expressing the integrand \( \frac{z + 1}{z(z^2 + 4)} \) as a sum of partial fractions. Since the denominator factors into \( z \) and \( z^2 + 4 \), set up the decomposition as \( \frac{z + 1}{z(z^2 + 4)} = \frac{A}{z} + \frac{Bz + C}{z^2 + 4} \).
Multiply both sides of the equation by the denominator \( z(z^2 + 4) \) to clear the fractions, resulting in \( z + 1 = A(z^2 + 4) + (Bz + C)z \).
Expand the right-hand side to get \( z + 1 = A z^2 + 4A + B z^2 + C z \), then group like terms: \( (A + B) z^2 + C z + 4A \).
Equate the coefficients of corresponding powers of \( z \) on both sides: For \( z^2 \), \( A + B = 0 \); for \( z \), \( C = 1 \); and for the constant term, \( 4A = 1 \). Solve this system to find \( A, B, \) and \( C \).
Rewrite the integral using the partial fractions found, then integrate each term separately: \( \int \frac{A}{z} dz + \int \frac{Bz + C}{z^2 + 4} dz \). Use standard integral formulas such as \( \int \frac{1}{z} dz = \ln|z| + C \) and for the second integral, consider splitting it into two integrals and using substitution or recognizing the form \( \int \frac{z}{z^2 + a^2} dz \) and \( \int \frac{1}{z^2 + a^2} dz \).

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