Chapter 1: Problem 7
Find a function \(y=f(x)\) satisfying the given differential equation and the prescribed initial condition. \(\frac{d y}{d x}=\frac{10}{x^{2}+1} ; y(0)=0\)
Short Answer
Expert verified
The function is \( y(x) = 10 \cdot \tan^{-1}(x) \).
Step by step solution
01
Identify the Differential Equation
The given problem is a differential equation \( \frac{d y}{d x} = \frac{10}{x^2 + 1} \). Our goal is to find a function \( y = f(x) \) that satisfies this equation, along with an initial condition \( y(0) = 0 \).
02
Integrate the Differential Equation
To solve for \( y \), integrate both sides of the equation with respect to \( x \). The integral of \( \frac{d y}{d x} \) is simply \( y(x) \). Thus, \[ y(x) = \int \frac{10}{x^2 + 1} \, dx. \] Recognize that this integral is the standard form of \( \tan^{-1}(x) \), which gives us,\[ y(x) = 10 \cdot \tan^{-1}(x) + C, \]where \( C \) is a constant of integration.
03
Apply the Initial Condition
We use the initial condition \( y(0) = 0 \) to solve for \( C \). Substitute \( x = 0 \) and \( y = 0 \) into the equation\[ 0 = 10 \cdot \tan^{-1}(0) + C. \]Since \( \tan^{-1}(0) = 0 \), it simplifies to \[ 0 = 0 + C. \]Thus, \( C = 0 \).
04
Write the Final Function
With \( C = 0 \), our solution follows:\[ y(x) = 10 \cdot \tan^{-1}(x). \]This function satisfies both the differential equation and the initial condition.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Integration Techniques
Integration is a fundamental technique used to solve differential equations. In our exercise, we deal with the differential equation \( \frac{d y}{d x} = \frac{10}{x^2 + 1} \). To solve this, we need to integrate the right-hand side with respect to \( x \). This process involves recognizing standard integral forms and then computing these integrals to find the function \( y(x) \).
\( \int \frac{10}{x^2 + 1} \, dx \) is transformed into \( 10 \cdot \int \frac{1}{x^2 + 1} \, dx \), which corresponds to \( 10 \cdot \tan^{-1}(x) \), a standard integration result from calculus. This technique highlights the importance of recognizing integral forms to efficiently solve differential equations.
Look out for:
\( \int \frac{10}{x^2 + 1} \, dx \) is transformed into \( 10 \cdot \int \frac{1}{x^2 + 1} \, dx \), which corresponds to \( 10 \cdot \tan^{-1}(x) \), a standard integration result from calculus. This technique highlights the importance of recognizing integral forms to efficiently solve differential equations.
Look out for:
- Rewriting equations to resemble a standard integration form
- Utilizing known integrals for quick computation
Initial Value Problems
Initial value problems involve finding a function that satisfies a differential equation and a given starting point or condition. In our example, we see the initial condition \( y(0) = 0 \) paired with the differential equation \( \frac{d y}{d x} = \frac{10}{x^2 + 1} \).
This initial condition allows us to determine any constants of integration that appear when solving the integral. After solving the integral, we have \( y = 10 \cdot \tan^{-1}(x) + C \), where \( C \) is an unknown constant. Applying the given initial condition helps us find \( C \): Substitute \( x = 0 \) and \( y = 0 \) into the equation, leading to \( C = 0 \).
Approach these problems by:
This initial condition allows us to determine any constants of integration that appear when solving the integral. After solving the integral, we have \( y = 10 \cdot \tan^{-1}(x) + C \), where \( C \) is an unknown constant. Applying the given initial condition helps us find \( C \): Substitute \( x = 0 \) and \( y = 0 \) into the equation, leading to \( C = 0 \).
Approach these problems by:
- Solving the differential equation through integration
- Using given initial conditions to determine constants
Analytic Solutions
Analytic solutions provide explicit expressions for functions solving differential equations. This method of solving reveals a clear, precise form of the solution as opposed to numerical or approximate solutions.
In our case, we start with the differential equation \( \frac{d y}{d x} = \frac{10}{x^2 + 1} \). By integrating, we find an expression for \( y \). Here, it's \( y(x) = 10 \cdot \tan^{-1}(x) + C \). We then apply the initial value \( y(0) = 0 \) to specifically solve for \( C \), resulting in \( C = 0 \). Therefore, our analytic solution to the initial value problem is \( y(x) = 10 \cdot \tan^{-1}(x) \).
Benefits of analytic solutions include:
In our case, we start with the differential equation \( \frac{d y}{d x} = \frac{10}{x^2 + 1} \). By integrating, we find an expression for \( y \). Here, it's \( y(x) = 10 \cdot \tan^{-1}(x) + C \). We then apply the initial value \( y(0) = 0 \) to specifically solve for \( C \), resulting in \( C = 0 \). Therefore, our analytic solution to the initial value problem is \( y(x) = 10 \cdot \tan^{-1}(x) \).
Benefits of analytic solutions include:
- They offer exact and specific results
- Solutions can be easily interpreted and applied