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Ch. 9 - First-Order Differential Equations
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077당신이 사용하는 게 아니라요?교과서 변경
9장, 문제 9.PE.26

In Exercises 23–28, solve the initial value problem.
x dy + (y - cos x) dx = 0, y(π/2) = 0

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Rewrite the given differential equation in the form \( M(x,y) \, dx + N(x,y) \, dy = 0 \). Here, the equation is \( x \, dy + (y - \cos x) \, dx = 0 \), so rearranged as \( (y - \cos x) \, dx + x \, dy = 0 \).
Check if the differential equation is exact by computing the partial derivatives \( \frac{\partial M}{\partial y} \) and \( \frac{\partial N}{\partial x} \), where \( M = y - \cos x \) and \( N = x \). If they are equal, the equation is exact.
If the equation is exact, find the potential function \( \Psi(x,y) \) such that \( \frac{\partial \Psi}{\partial x} = M = y - \cos x \) and \( \frac{\partial \Psi}{\partial y} = N = x \). Integrate \( M \) with respect to \( x \) to find \( \Psi(x,y) \) up to a function of \( y \).
Differentiate the expression for \( \Psi(x,y) \) with respect to \( y \) and set it equal to \( N = x \) to determine the function of \( y \) introduced during integration.
Use the initial condition \( y(\pi/2) = 0 \) to find the constant of integration in the implicit solution \( \Psi(x,y) = C \), and write the final implicit solution to the initial value problem.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Initial Value Problem (IVP)

An initial value problem involves solving a differential equation with a given condition specifying the value of the unknown function at a particular point. This condition helps determine the unique solution that fits the problem's context.
추천 영상:
05:03
Initial Value Problems

Exact Differential Equations

An exact differential equation can be written in the form M(x,y)dx + N(x,y)dy = 0, where there exists a function F(x,y) such that dF = M dx + N dy. Recognizing exactness allows solving by finding this potential function F.
추천 영상:
07:39
Classifying Differential Equations

Integrating Factor

When a differential equation is not exact, an integrating factor is a function used to multiply the equation to make it exact. Finding the correct integrating factor simplifies solving the equation by enabling the use of exact equation methods.
추천 영상:
06:18
Integration by Parts for Definite Integrals