- #1

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D2(f) + f = 3*D(a) where Da stands for the a'd derivative

So is there any quick way to solve this? I also can't seem to find a formula for the n'd derivative.

Thanks!

- Thread starter JanClaesen
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- #1

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D2(f) + f = 3*D(a) where Da stands for the a'd derivative

So is there any quick way to solve this? I also can't seem to find a formula for the n'd derivative.

Thanks!

- #2

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Hello,

What are you trying to do here? Are you trying to find the derivative of

D2(f) + f = 3*D(a) where Da stands for the a'd derivative

So is there any quick way to solve this? I also can't seem to find a formula for the n'd derivative.

Thanks!

sin(2x)^(-0.5) ?

What is a'd derivative?

Thanks

Matt

- #3

tiny-tim

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(have a pi: π and a square-root: √ )

(we say the

D2(f) + f = 3*D(a) where Da stands for the a'd derivative

So is there any quick way to solve this? I also can't seem to find a formula for the n'd derivative.

Thanks!

Do you mean "what is the nth derivative of 1/√(sin2x)?"

And what is f?

- #4

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Hello , I'm sorry if I was a little unclear:

So there is a certain relation for the function sin(2x)^(-1/2): the second derivative of this function plus the function itself gives the (n'th derivative)*3, the question is to determine n.

- #5

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Rephrase:

If [itex]y=1/\sqrt{sin(2x)} \text{ and }y''+y=3y^{(n)}[/itex], solve for

I have hammered out the first 10 derivatives of

N.B.: The expression on the left of the differential equation is

[tex]\frac{3}{(sin(2x))^{5/2}}.[/tex]

--Elucidus

- #6

tiny-tim

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Hi JanClaesen! Hi Elucidus!If [itex]y=1/\sqrt{sin(2x)} \text{ and }y''+y=3y^{(n)}[/itex], solve forn. (Note [itex]y^{(n)} = \frac{d^n y}{{dx}^n}[/itex].)

I don't think there can be a solution …

just try to solve 3y

that gives you a characteristic equation, of which 1/√sin

- #7

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I think the exercise is correct, it's probably just me who misunderstood it, I scanned it so you guys can have a look at it: http://img212.imageshack.us/img212/2451/scan001001s.jpg [Broken]

It's exercice 17a, the answer should be 5, perhaps alpha is a power?

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- #8

tiny-tim

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D'oh!I think the exercise is correct, it's probably just me who misunderstood it, I scanned it so you guys can have a look at it: http://img212.imageshack.us/img212/2451/scan001001s.jpg [Broken]

It's exercice 17a, the answer should be 5, perhaps alpha is a power?

Yes of course α is a power … Question 17a

f'' + f = 3f

Why did you write D2(f) + f = 3*D(a) in your first post??

ok, since f = 1/√(sin(2x)), what is f'' + f?

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- #9

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Because I only thought of that while I was writing the newest post

I'm sorry, but I never saw a power-variable being named alpha before, that's why I thought it was perhaps a way to note the n'th derivative, which seemed to me like a quite hard thing to solve.

Hope I didn't waste too much of your time!

- #10

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Just curious ... what language is that question written in ... and are you from the Netherlands ?

- #11

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Hah nice, you're right, it's Dutch , but I'm not from the Netherlands but from its little brother, Belgium. Most people here are American I guess?

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