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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:
  • Rewriting equations to resemble a standard integration form
  • Utilizing known integrals for quick computation
Effective integration techniques are crucial in transforming differential equations into understandable solutions.
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:
  • Solving the differential equation through integration
  • Using given initial conditions to determine constants
Properly applying initial value conditions ensures the resulting function accurately fits all given criteria.
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:
  • They offer exact and specific results
  • Solutions can be easily interpreted and applied
Getting an analytic solution allows us to thoroughly comprehend the behavior of the function within the context of the problem.

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Most popular questions from this chapter

Problems deal with a shallow reservoir that has a one-square-kilometer water surface and an average water depth of 2 meters. Initially it is filled with fresh water, but at time \(t=0\) water contaminated with a liquid pollutant begins flowing into the reservoir at the rate of 200 thousand cubic meters per month. The well-mixed water in the reservoir flows out at the same rate. Your first task is to find the amount \(x(t)\) of pollutant (in millions of liters) in the reservoir after 1 months. The incoming water has a pollutant concentration of \(c(t)=10\) liters per cubic meter \(\left(\mathrm{L} / \mathrm{m}^{3}\right)\). Verify that the graph of \(x(t)\) resembles the steadily rising curve in Fig. 1.5.9, which approaches asymptotically the graph of the equilibrium solution \(x(t)=20\) that corresponds to the reservoir's long-term pollutant content. How long does it take the pollutant concentration in the reservoir to reach \(10 \mathrm{~L} / \mathrm{m}^{3} ?\)

A 400 -gal tank initially contains 100 gal of brine containing 50 lb of salt. Brine containing 1 lb of salt per gallon enters the tank at the rate of \(5 \mathrm{gal} / \mathrm{s}\), and the well-mixed brine in the tank flows out at the rate of \(3 \mathrm{gal} / \mathrm{s}\). How much salt will the tank contain when it is full of brine?

$$ x y^{\prime}=y+\sqrt{x^{2}+y^{2}} $$

Consider a reservoir with a volume of 8 billion cubic feet (ft \(^{3}\) ) and an initial pollutant concentration of \(0.25 \%\). There is a daily inflow of 500 million \(\mathrm{ft}^{3}\) of water with a pollutant concentration of \(0.05 \%\) and an equal daily outflow of the well-mixed water in the reservoir. How long will it take to reduce the pollutant concentration in the reservoir to \(0.10 \%\) ?

Show that the substitution \(v=a x+b y+c\) transforms the differential equation \(d y / d x=F(a x+b y+c)\) into a separable equation.

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