Homogeneous linear ODEs with Constant Coefficients

In summary, the conversation is discussing the possibility of finding a nontrivial function whose derivative is a constant multiple of itself. It is mentioned that an exponential function is the only nontrivial function that satisfies this criteria. However, it is also noted that the function $y = \sin x$ can also work, as it satisfies the equation $y'' + y = 0$. It is mentioned that as long as the boundaries are not $y'(0) = 0$ and $y'(\frac{\pi}{2}) = 0$, then $y = A\sin x + B\cos x = e^0(A\sin x + B\cos x)$ is also a solution.
  • #1
oasi
14
0
do you have a idea about it?can you help me

http://img17.imageshack.us/img17/1156/18176658.png
 
Physics news on Phys.org
  • #2
oasi said:
do you have a idea about it?can you help me

http://img17.imageshack.us/img17/1156/18176658.png

For example, take $ay' + by = 0$. Solving for y' yields
$$
y' = -\frac{b}{a}y = ky
$$
where k = -b/a.

The only nontrivial function whose derivative is a constant multiple of itself is an exponential function.
 
  • #3
But $y = \sin x$ could work. For example,

$y'' + y = 0$

has as one solution $y = \sin x$.
 
  • #4
Jester said:
But $y = \sin x$ could work. For example,

$y'' + y = 0$

has as one solution $y = \sin x$.

As long as the boundaries aren't $y'(0) = 0$ and $y'\left(\frac{\pi}{2}\right) = 0$ then y = 0. :)

But $y = A\sin x + B\cos x = e^0\left(A\sin x + B\cos x\right)$ is also a solution of the non boundary value problem.
 
  • #5


Yes, I am familiar with homogeneous linear ODEs with constant coefficients. These types of equations have the form dy/dx + ay = 0, where a is a constant. They are called "homogeneous" because the equation only contains the dependent variable y and its derivatives, and "linear" because the equation is linear in y and its derivatives. These types of equations are commonly used in physics, engineering, and other scientific fields to model various systems.

To solve a homogeneous linear ODE with constant coefficients, we can use the method of separation of variables or the method of undetermined coefficients. In both cases, we can find a general solution by solving for the dependent variable y in terms of the independent variable x.

If you need help with a specific problem or concept related to homogeneous linear ODEs with constant coefficients, I would be happy to assist you. It may be helpful to provide more context or information about the problem you are working on.
 

FAQ: Homogeneous linear ODEs with Constant Coefficients

1. What is a homogeneous linear ODE with constant coefficients?

A homogeneous linear ODE (ordinary differential equation) with constant coefficients is a type of differential equation where the dependent variable and its derivatives are linearly related, and the coefficients of the terms are constants. The term "homogeneous" means that all the terms in the equation have the same degree, and therefore, there is no constant term present.

2. How do you solve a homogeneous linear ODE with constant coefficients?

To solve a homogeneous linear ODE with constant coefficients, you can use the method of undetermined coefficients or the method of variation of parameters. In both methods, you will first need to find the characteristic equation by setting the coefficients of the derivatives equal to zero. Then, depending on the method, you will find the particular solution by substituting in a guessed solution or using a set of integrals.

3. What is the significance of constant coefficients in a homogeneous linear ODE?

The presence of constant coefficients in a homogeneous linear ODE means that the solution will have exponential functions as a part of its general solution. This makes the problem easier to solve as exponential functions have simple derivatives and integrals. Additionally, constant coefficients make the solution more stable and predictable, as they do not change with respect to the independent variable.

4. How are homogeneous linear ODEs with constant coefficients used in science and engineering?

Homogeneous linear ODEs with constant coefficients are used in many areas of science and engineering to model phenomena that exhibit exponential growth or decay. For example, in physics, these equations are used to describe the behavior of electrical circuits and simple harmonic oscillators. In chemistry, they are used to model the kinetics of chemical reactions. In economics, they are used to analyze population growth and interest rates.

5. Can a homogeneous linear ODE with constant coefficients have complex solutions?

Yes, a homogeneous linear ODE with constant coefficients can have complex solutions. This happens when the roots of the characteristic equation are complex numbers. In this case, the general solution will involve complex exponential functions. However, for real-world applications, these complex solutions are usually simplified to real-valued solutions, as they have no physical meaning.

Back
Top