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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.PE.125

In Exercises 125–128 solve the differential equation.
125. dy/dx = √y cos(√y)

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1
Rewrite the differential equation \( \frac{dy}{dx} = \sqrt{y} \cos(\sqrt{y}) \) to separate variables. Express it as \( \frac{dy}{\sqrt{y} \cos(\sqrt{y})} = dx \).
Make the substitution \( u = \sqrt{y} \), which implies \( y = u^2 \) and \( dy = 2u \, du \).
Rewrite the left side integral in terms of \( u \): \( \frac{dy}{\sqrt{y} \cos(\sqrt{y})} = \frac{2u \, du}{u \cos(u)} = \frac{2 \, du}{\cos(u)} \).
Set up the integral \( \int \frac{2}{\cos(u)} \, du = \int dx \), which simplifies to \( 2 \int \sec(u) \, du = x + C \), where \( C \) is the constant of integration.
Integrate \( \sec(u) \) using the standard formula \( \int \sec(u) \, du = \ln | \sec(u) + \tan(u) | + C \), then substitute back \( u = \sqrt{y} \) to express the solution implicitly.

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