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Homework Statement
Solve:
[itex] \frac{d^{2}y}{dx^{2}} + \omega^{2}y = 0 [/itex]
Show that the general solution can be written in the form:
[itex] y(x) = A\sin(\omega x + \alpha) [/itex]
Where A and alpha are arbitrary constants
Homework Equations
The Attempt at a Solution
I know that I will need to change variables for this problem, so I let
[itex] v = \frac{dy}{dx} [/itex]
Then, using the chain rule I found:
[itex] \frac{d^{2}y}{dx^{2}} = \frac{dv}{dx} = \frac{dv}{dy}\frac{dy}{dx} = v\frac{dv}{dy} [/itex]
Substituting this into the equation I found:
[itex] v\frac{dv}{dy} + \omega^{2} y = 0 [/itex]
This looks to me like a separable equation, so I made the following separation:
[itex] v\frac{dv}{dy} = -\omega^{2} y [/itex]
[itex] vdv = -\omega^{2} ydy[/itex]
I integrated both sides and obtained:
[itex] \frac{v^2}{2} = -\omega^{2} \frac{y^2}{2}[/itex]
After some manipulation I obtained:
[itex] v = +- sqrt(2(-\frac{\omega^{2}y}{2} + C)) [/itex]
Since:
[itex] v = \frac{dy}{dx} [/itex]
I made that substitution and found that:
[itex] \frac{dy}{dx} = +- sqrt(2-\frac{\omega^{2}y}{2} + C)) [/itex]
However, I am a little unsure of myself when it comes to problems like this, so I just wanted to see if I was on the right track with this problem or completely off base. My next step would be to integrate that square root, but I don't see how that would give me anything close to what the book wants for an answer.
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