Date: Jan 5, 2013 1:08 AM Author: William Elliot Subject: Re: Off Topic Physics/math question On Fri, 4 Jan 2013, wrschlanger@gmail.com wrote:

> If y(x) = 1 / x

> then y(x) > 0 when x > 0 and y(x) < 0 when x < 0.

>

> According to the power rule of Calculus, y'(x) = -1 / x^2.

> So y'(x) is always negative.

>

> Are we losing information by taking the derivative?

Yes, f(x) = 1/x + c has the same derivative.