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APM346-2016F => APM346--Lectures => Chapter 2 => Topic started by: Arush Mitra on September 21, 2016, 01:59:17 PM

Title: section 2.1
Post by: Arush Mitra on September 21, 2016, 01:59:17 PM
could someone please explain how do we get from equation 1 to equation 2. please check the attached file to view the equations.
thanks in advance
Title: Re: section 2.1
Post by: Victor Ivrii on September 21, 2016, 04:55:42 PM
No, we do not get equation (2) from (1) but we observe that if (1) holds and we take $dx$, $dt$ satisfying (1) then
\begin{equation}
du=u_tdt +u_xdx= (u_t a + u_xb)\frac{dt}{a}=0.
\end{equation}