# Thread: Find the differential of a function

1. ## Find the differential of a function

Find the differential of :

Find dy.

I'm not sure what the 'differential' means, or how to find dy.

Thanks.

2. Originally Posted by TSizzle55
Find the differential of :

Find dy.

I'm not sure what the 'differential' means, or how to find dy.

Thanks.
why didn't you look it up in your text?

the differential dy is given by:

$dy = f'(x) ~dx$

3. Originally Posted by TSizzle55
Find the differential of :

Find dy.

I'm not sure what the 'differential' means, or how to find dy.

Thanks.
A differential is defined as $\,dy=f'(x)\,dx$

In essence, you find $\frac{\,dy}{\,dx}=f'(x)$, and then multiply both sides by $\,dx$ to get the equation I defined above.

Can you try to do the problem now?

--Chris

4. A differential is defined as

In essence, you find , and then multiply both sides by to get the equation I defined above.

Can you try to do the problem now?

Yes, I get dy = x(3xcos(3x) + 2sin(3x)) dx

But how do I find dx? In other words, I need dy without dx anywhere in the equation. Is it possible to substitute something in for dx?

5. Originally Posted by TSizzle55
A differential is defined as

In essence, you find , and then multiply both sides by to get the equation I defined above.

Can you try to do the problem now?

Yes, I get dy = x(3xcos(3x) + 2sin(3x)) dx

But how do I find dx? In other words, I need dy without dx anywhere in the equation. Is it possible to substitute something in for dx?
Yes, its possible. They usually give the value of $\,dx$ in the problem.

--Chris