Solving a differential equation

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Homework Help Overview

The discussion revolves around finding the particular solution of a differential equation involving the function y and its derivative, with a specific initial condition provided.

Discussion Character

  • Exploratory, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to solve the differential equation by separating variables and integrating. They express uncertainty about their setup and whether they made a mistake in their calculations. Other participants inquire about further simplification of the solution.

Discussion Status

Some participants provide feedback on the original poster's steps, indicating no flaws in the calculations but suggesting simplification. There is an ongoing exploration of how to simplify the solution further, with participants discussing properties of exponents and logarithms.

Contextual Notes

The original poster expresses uncertainty about their approach and the correctness of their solution, indicating a need for clarification on the simplification process.

hardatwork
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Homework Statement


Find the particular solution of the differential equation
[tex]\frac{dy}{dx}[/tex]+ycos(x)=3cos(x)


Homework Equations



y(0)=5

The Attempt at a Solution


[tex]\frac{dy}{dx}[/tex]=3cos(x)-ycos(x)
[tex]\frac{dy}{dx}[/tex]=(cos(x))(3-y)
[tex]\int \frac{dy}{3-y}[/tex]=[tex]\int cos(x) dx[/tex]
-ln|3-y|=sin(x)+C
ln|3-y|=-sin(x)-C

to find C, I did
ln|3-5|=-sin(0)-C
ln|-2|=-C
C=-ln|2|
So the equation is
3-y=e(-sin(x)+ln|2|)
-y=e(-sin(x)+ln|2|)-3
y=-e(-sin(x)+ln|2|)+3
But this is incorrect. I'm not sure if my setup is right or if I made a mistake. I would greatly appreciate if someone could see were I went wrong.
 
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Your steps and your solution have no flaws. However, you can simplify your solution further. Also, it is not necessary to continue using the absolute value signs when the argument is positive.
 
How would I simplify futher?
 
hardatwork said:
How would I simplify futher?

Remember that [itex]a^{b+c} = a^ba^c[/itex] and that the exponential function is the inverse function of the natural logarithm.
 
Oh! Okay that makes. Thank You so much!
 

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