# The chain rule

1. Mar 31, 2009

### Niles

1. The problem statement, all variables and given/known data
Hi all.

I have an expression given by V(x,y) = ay+x2y2, where a is a constant. I wish to find the time-derivative of V(x,y), and this is what I have done:

$$\frac{dV}{dt} = a\dot y + \frac{d}{dt}x^2y^2,$$
where the dot over y represents differentiation w.r.t. time. My problem is the last term, and I wish to use the chain-rule, but I am not sure how to use it. Can you give me a push in the right direction?

Best regards,
Niles.

2. Mar 31, 2009

### rootX

Apply the product rule first to x^2.y^2

3. Mar 31, 2009

### Nick89

Do you know how to do:
$$\frac{d}{dt}x^2$$
(Assuming x is a fuction of t)
?