# I know the answer but I don't know why!

1. Jun 19, 2005

### Brewer

I have a question that asks me to write dv/dt as a function of x.

I know that dv/dt = vdv/dx

but I don't know why this is. Could anybody shed some light on this for me? Just so I understand why it is this!!!

Thanks in advance

2. Jun 19, 2005

### dextercioby

Did you hear about the chain rule of differentiation...?

Daniel.

3. Jun 19, 2005

### Brewer

yeah that though occured to me whilst sitting in the car just.

but surely theres another term involved in it isn't there?

4. Jun 19, 2005

### dextercioby

No.

$$\frac{dv}{dt}=\frac{dv}{dx}\frac{dx}{dt}$$.

Daniel.

5. Jun 19, 2005

### Brewer

Of course!! What I had in mind was the product rule! Thank you for that - makes so much sense to me now!!!

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