Re: derivative

In article <Y7Sae.1992$pk5.339@fed1read02>, "vsgdp" <spam@xxxxxxxx>
wrote:

> If I have a function f(x, y), where x = x(t) and y = y(t), is this the
> correct way to take the derivative wrt to t?
>
> d/dt( -x / (x^2 + y^2) )
>
> = [(x^2 + y^2)(-dx/dt) + x(2x(dx/dt) + 2y(dy/dt))] / (x^2 + y^2)^2
>
> ?

Looks OK.
.