Differential Equation-Separable Equations

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The discussion focuses on solving the differential equation given by the equation xcos(x) = (2y + e^(3y)) y' with the initial condition y(0) = 0. The correct family of solutions is identified as xsin(x) + cos(x) = y^2 + e^(3y) + C, correcting a sign error from the initial attempt. Participants clarify the importance of substituting both x and y values into the equation based on the initial conditions provided, emphasizing the need to understand the roles of dependent and independent variables in different contexts.

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Homework Statement


Find the solution of the diff eq that satisfies the given initial coordinate


Homework Equations


xcosx=(2y + e^(3y)) y' , y(0)=0


The Attempt at a Solution



So I have the family of solutions:
xsinx-cosx=y^2 + e^(3y)/3 + c

and I know to put 0 in for the x's, but the solution is wrong, and it appears like I need to put 0 into the y's (yes I did say y's) but not sure why.
 
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neshepard said:

Homework Statement


Find the solution of the diff eq that satisfies the given initial coordinate


Homework Equations


xcosx=(2y + e^(3y)) y' , y(0)=0


The Attempt at a Solution



So I have the family of solutions:
xsinx-cosx=y^2 + e^(3y)/3 + c

and I know to put 0 in for the x's, but the solution is wrong, and it appears like I need to put 0 into the y's (yes I did say y's) but not sure why.
Yes, substitute 0 for x and 0 for y. That's what y(0) = 0 means.

You have a sign error in your solution. It should be xsinx + cosx = y^2 + e^(3y) + C.
 
Thanks for the reply. And just to clarify, I have another problem where the initial condition is u(0)=-5 so I put in -5 for my x's and 0 for my y's?
 
neshepard said:
Thanks for the reply. And just to clarify, I have another problem where the initial condition is u(0)=-5 so I put in -5 for my x's and 0 for my y's?

If x is the dependent variable, that is, you have u(x), then you need to set x=0 and u=-5. You don't have x and y anymore, one of them has been replaced by a new function u in this other problem.
 
Nice...thanks.
 

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