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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 8.5.70

Solve the initial value problems in Exercises 67–70 for x as a function of t.
(t + 1) (dx/dt) = x² + 1 (for t > -1), x(0) = 0

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Rewrite the given differential equation \((t + 1) \frac{dx}{dt} = x^{2} + 1\) to isolate \(\frac{dx}{dt}\): \(\frac{dx}{dt} = \frac{x^{2} + 1}{t + 1}\).
Recognize that this is a separable differential equation. Rearrange terms to separate variables \(x\) and \(t\): \(\frac{dx}{x^{2} + 1} = \frac{dt}{t + 1}\).
Integrate both sides: \(\int \frac{dx}{x^{2} + 1} = \int \frac{dt}{t + 1}\).
Evaluate the integrals: The left integral is \(\arctan(x)\), and the right integral is \(\ln|t + 1| + C\), where \(C\) is the constant of integration. So, \(\arctan(x) = \ln|t + 1| + C\).
Use the initial condition \(x(0) = 0\) to find \(C\): Substitute \(t=0\) and \(x=0\) into the equation to solve for \(C\), then express \(x\) explicitly as a function of \(t\) by taking the tangent of both sides.

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