Can't determine the correct integrating factor (DE)

In summary, to solve the given equation using an integrating factor, the equation was first put into standard form. However, in order to find the integrating factor, the y variable needs to be eliminated from the sine and cosine terms. This can be done by simplifying the equation to dy/dx + (x+2/x)tan y = 0. From there, the integrating factor can be found by taking the antiderivative of the coefficient of the y term, which results in mu(x) = x e^(int 2/x tan y)dx.
  • #1
darryw
127
0

Homework Statement



Solve (x+2)sin y dx + xcos y dy = 0 by finding integrating factor mu(x)

Homework Equations



i put equation in standard form to get integrating factor

dy/dx + (x+2)sin y / x cos y = 0

but don't i need to get the y out of the sin and cos somehow?

so that y' + p(x)y = q(x)

I could simplify into dy/dx + (x+2/x)tan y = 0 but not sure if that even helps.

I am stuck please help, thanks

The Attempt at a Solution


 
Physics news on Phys.org
  • #2
dy/dx + (x+2)sin y / x cos y = 0 y' + (x+2)sin y / x cos y = 0 p(x)= (x+2)sin y / x cos y q(x) = 0 mu(x) = e^(int p(x) dx)mu(x) = e^ (int (x+2)sin y/xcos y)dx = e^ (int (x+2)/x tan y)dx = e^ (int 1/x tan y)dx + e^ (int 2/x tan y)dx = e^ (ln |x| + int 2/x tan y)dx
 

FAQ: Can't determine the correct integrating factor (DE)

What is an integrating factor in a differential equation?

An integrating factor is a function that is used to solve a differential equation by multiplying it to both sides of the equation. This helps to simplify the equation and make it easier to solve.

Why is it sometimes difficult to determine the correct integrating factor?

The process of determining the correct integrating factor can be difficult because it involves finding a function that satisfies a specific condition. This condition is known as the integrating factor equation, and it can be challenging to solve for the correct function.

What are some methods for determining the correct integrating factor?

There are a few methods that can be used to determine the correct integrating factor, such as the method of variation of parameters, the method of undetermined coefficients, and the method of reduction of order.

Can an incorrect integrating factor be used to solve a differential equation?

Yes, an incorrect integrating factor can still be used to solve a differential equation, but it may lead to a more complicated solution or an incorrect solution altogether. It is essential to determine the correct integrating factor to ensure an accurate solution.

Are there any resources that can help with determining the correct integrating factor?

Yes, there are many online resources and textbooks that provide step-by-step instructions and examples for determining the correct integrating factor. Additionally, seeking help from a tutor or instructor can also be beneficial.

Back
Top