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

#### 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!!!

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#### dextercioby

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

Daniel.

#### Brewer

dextercioby said:
Did you hear about the chain rule of differentiation...?

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

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

#### dextercioby

Homework Helper
No.

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

Daniel.

#### Brewer

dextercioby said:
No.

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

Daniel.
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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